PASCO EM-8656 User Manual

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Includes

Teacher's Notes

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Typical

Experiment

Results

AC/DC ELECTRONICS

Instruction Manual and Experiment Guide for the PASCO scientific Model EM-8656

LABORATORY

012-05892A

1/96

012-05892A AC/DC Electronics Laboratory

T able of Contents

Section...........................................................................................................Page

Introduction .....................................................................................................1

Equipment........................................................................................................1

Getting Started.................................................................................................2

Notes on the Circuits Experiment Board.........................................................3

The Experiments..............................................................................................4

Comments on Meters.......................................................................................4

Experiments

Experiment 1: Circuits Experiment Board .......................................5

Experiment 2: Lights in Circuits ......................................................7

Experiment 3: Ohm's Law ................................................................9

Experiment 4: Resistances in Circuits ............................................11

Experiment 5: Voltages in Circuits ................................................15

Experiment 6: Currents in Circuits.................................................19

Experiment 7: Kirchhoff's Rules ....................................................21

Experiment 8: Capacitors in Circuits..............................................23

Experiment 9: Diodes .....................................................................25

Experiment 10: Transistors...............................................................27

Computer Experiments

Experiment 11: Ohm’s Law II..........................................................29

Experiment 12: RC Circuit ...............................................................37

Experiment 13: LR Circuit ...............................................................43

Experiment 14: LRC Circuit.............................................................49

Experiment 15: Diode Lab – Part 1 ..................................................57

Experiment 16: Diode Lab – Part 1 ..................................................67

Experiment 17: Transistor Lab 1 – The NPN Transistor

as a Digital Switch..........................................................................85

Experiment 18: Transistor Lab 2 – Current Gain:

The NPN Emitter-Follower Amplifier ..........................................93

Experiment 19: Transistor Lab 3 – Common Emitter Amplifier ...101

Experiment 20: Induction – Magnet Through a Coil .....................109

Appendix: Tips and Troubleshooting .........................................................113

Teacher's Guide ...........................................................................................115

Technical Support................................................................................ Back Cover

AC/DC Electronics Laboratory 012-05892A

Please—Feel free to duplicate this manual subject to the copyright restrictions below.

The PASCO scientific Model EM-8656 AC/DC Electronics Laboratory manual is copyrighted and all rights reserved. However, permission is granted to non-profit educational institutions for reproduction of any part of this manual providing the reproductions are used only for their laboratories and are not sold for profit. Reproduction under any other circumstances, without the written consent of PASCO scientific, is prohibited.

Limited Warranty

PASCO scientific warrants this product to be free from defects in materials and workmanship for a period of one year from the date of shipment to the customer. PASCO will repair or replace, at its option, any part of the product which is deemed to be defective in material or workmanship. This warranty does not cover damage to the product caused by abuse or improper use. Determination of whether a product failure is the result of a manufacturing defect or improper use by the customer shall be made solely by PASCO scientific. Responsibility for the return of equipment for warranty repair belongs to the customer. Equipment must be properly packed to prevent damage and shipped postage or freight prepaid. (Damage caused by improper packing of the equipment for return shipment will not be covered by the warranty.) Shipping costs for returning the equipment, after repair, will be paid by PASCO scientific.

Equipment Return

Should the product have to be returned to PASCO scientific for any reason, notify PASCO scientific by letter, phone, or fax BEFORE returning the product. Upon notification, the return authorization and shipping instructions will be promptly issued.

NOTE: NO EQUIPMENT WILL BE

ACCEPTED FOR RETURN WITHOUT AN AUTHORIZATION FROM PASCO.

When returning equipment for repair, the units must be packed properly. Carriers will not accept responsibility for damage caused by improper packing. To be certain the unit will not be damaged in shipment, observe the following rules:

➀ The packing carton must be strong enough for the

item shipped.

➁ Make certain there are at least two inches of

packing material between any point on the apparatus and the inside walls of the carton.

➂ Make certain that the packing material cannot shift

in the box or become compressed, allowing the instrument come in contact with the packing carton.

Credits

This manual authored by: Ann Hanks and Dave Griffith

Address: PASCO scientific

10101 Foothills Blvd. Roseville, CA 95747-7100

Phone: (916) 786-3800 FAX: (916) 786-3292 email: techsupp@pasco.com web: www.pasco.com

012-05892A AC/DC Electronics Laboratory

Introduction

The EM-8656 AC/DC Electronics Laboratory is designed for both DC and AC electricity experiments. The circuit board can be powered by batteries for DC experiments or it can be powered by a computer equipped with a Power Amplifier for AC experiments. The AC experiments could also be performed without a Power Amplifier if a function generator is available.

Equipment

The PASCO Model EM-8656 AC/DC Electronics Laboratory includes the following materials:

• Circuits Experiment Board

• Storage Case

• Component Bag

• Experiment Manual

The Circuit Experiment Board features:

The first ten experiments in this manual are DC experiments using battery power and multimeters rather than using a computer. The rest of the experiments use a computer (MAC or PC) with a Power Amplifier. The software used is Science Workshop™.

The Component Bag includes:

Resistors, 5%

(1) 33 Ω–– 5 watt (2) 10 Ω–– 1 watt (2) 4.7 Ω–– 1/2 watt (2) 100 Ω–– 1/2 watt (4) 330 Ω–– 1/2 watt (2) 560 Ω–– 1/2 watt (4) 1 KΩ–– 1/2 watt (2) 10 KΩ–– 1/2 watt (1) 100 KΩ–– 1/2 watt (1) 220 ΚΩ–– 1/2 watt (2) 22 KΩ–– 1/4 watt (1) 3.3 KΩ–– 1/4 watt

Capacitors

(2) Battery Holders, D-cell, (Batteries not included) (3) Light Sockets (3) #14 Light Bulbs – 2.5 V, 0.3 A* (1) Transistor Socket (1) Coil (Renco RL-1238-8200) (1) Resistor–– 3.3 Ω, 2W, 5% (36) Component springs (2) Banana Jacks (for power amplifier) (1) Potentiometer–– 25 Ω, 2W (1) Pushbutton switch

The Storage Case features:

(1) Cable clamp and 1/2" iron core

(1) 1 µF–– 35 volts (2) 10 µF–– 25 volts (1) 47 µF–– 50 volts (1) 470 µF–– 16 volts (1) 100 µF–– 16 volts (1) 330 µF–– 16 volts

(6) Diodes 1N-4007 (2) Transistors 2N-3904 (1 ea) LED red, green, yellow, bicolor Wire Leads––22 ga. (4@5" and 5 @10")

* NOTE: Due to manufacturer's tolerances, wattage may vary by 15-30% from bulb to bulb.

AC/DC Electronics Laboratory 012-05892A

Getting Started

➀ Store the components in the Ziplock bag until needed.

Keep track of, and return the components to the Ziplock bag after the experiment is completed.

➁ Identify the resistor value required for the individual

experiments with the help of the following chart.

➂ Familiarize yourself with the board layout, as shown.

Black Brown Red Orange Yellow Green Blue Violet Gray White

0 1 2 3 4 5 6 7 8 9

2nd Digit

1st Digit

Resistor Chart

➃ Students will need to use the same component layout

from one experiment to another. Labeling of the boards and your meters will enable students to more easily have continuity in their work. Using removable labels or using a permanent marker are two alternatives for marking the board.

No. of Zeros

Tolerance

Fourth Band

None Silver Gold Red

±20% ±10% ±5% ±2%

Pushbutton

switch

Battery Holder

(3) Light Bulbs

and Sockets

3 VOLT BULBS

ABC

–

Potentiometer3.3Ω ResistorTransistor socket

(for

Iron core)

KIT NO.

Coil

3.3Ω

3 VOLTS MAX

C W

Component

spring

Banana

Jacks

EM-8656

Board Layout

AC/DC ELECTRONICS LABORATORY

012-05892A AC/DC Electronics Laboratory

Notes on the Circuits Experiment Board

The springs are securely soldered to the board and serve as a convenient method for connecting wires, resistors and other components. Some of the springs are connected electrically to devices like the potentiometer and the D-cells. In the large Experimental Area, the springs are connected in pairs, oriented perpendicular to each other. This facilitates the connection of various types of circuits.

If a spring is too loose, press the coils together firmly to tighten it up. The coils of the spring should not be too tight, as this will lead to bending and/or breaking of the component leads when they are inserted or removed. If a spring gets pushed over, light pressure will get it straightened back up.

The components, primarily resistors, and small wires can be stored in the plastic bag supplied in the storage case. Encourage students to keep careful track of the components and return them to the bag each day following the lab period.

When connecting a circuit to a D-cell, note the polarity (+ or -) which is printed on the board. In some cases the polarity is not important, but in some it will be imperative. Polarity is very important for most meters.

Connections are made on the Circuits Experiment Board by pushing a stripped wire or a lead to a component into a spring. For maximum effect, the stripped part of the wire should extend so that it passes completely across the spring, making contact with the spring at four points. This produces the most secure electrical and mechanical connection.

Spring

Wire

Figure 1 Diagram of wires and springs

(top view)

(side view)

The Experiments

The experiments written up in this manual are developmental, starting from an introduction to the Circuits Experiment Board and complete circuits, through series and parallel circuits, ultimately resulting in diode and transistor characteristics. These experiments can be used in combination with existing labs that the teacher employs, or may be used as a complete lab unit.

Experiment 1 Circuits Experiment Board Experiment 2 Lights in Circuits Experiment 3 Ohm’s Law Experiment 4 Resistances in Circuits Experiment 5 Voltages in Circuits Experiment 6 Currents in Circuits Experiment 7 Kirchhoff’s Rules Experiment 8 Capacitors in Circuits Experiment 9 Diode Characteristics Experiment 10 Transistor Characteristics

Computer based experiments

Experiment 11 Ohm's Law II Experiment 12 RC Circuit Experiment 13 LR Circuit Experiment 14 LRC Circuit Experiment 15 Diodes Lab – Part 1 Experiment 16 Diodes Lab – Part 2 Experiment 17 Transistor Lab 1 Experiment 18 Transistor Lab 2 Experiment 19 Transistor Lab 3 Experiment 20 Induction, Magnet and Coil

Additional Equipment needed:

Please refer to the Equipment Needed section in the beginning of each experiment for a listing of all equipment requirements.

AC/DC Electronics Laboratory 012-05892A

Comments on Meters

VOM:

The Volt-Ohm-Meter or VOM is a multiple scale, multiple function meter (such as the PASCO SB-9623 Analog Multimeter), typically measuring voltage and resistance, and often current, too. These usually have a meter movement, and may select different functions and scales by means of a rotating switch on the front of the unit.

Advantages: VOM’s may exist in your laboratory and thus be readily accessible. A single meter may be used to make a variety of measurements rather than needing several meters.

Disadvantages: VOM’s may be difficult for beginning students to learn to read, having multiple scales corresponding to different settings. VOM’s are powered by batteries for their resistance function, and thus must be checked to insure the batteries are working well. Typically, VOM’s may have input resistances of 30,000 Ω on the lowest voltage range, the range that is most often used in these experiments. For resistances in excess of 1,000 Ω, this low meter resistance affects circuit operation during the taking of readings, and thus is not usable for the capacitor, diode and transistor labs.

DMM:

The Digital Multimeter or DMM is a multiple scale, multiple function meter (such as the PASCO SB-9624 Basic Digital Multimeter or the SE-9589 General Purpose DMM), typically measuring voltage and resistance, and often current, too. These have a digital readout, often with an LCD (Liquid Crystal Display). Different functions and scales are selected with either a rotating switch or with a series of pushbutton switches.

Advantages: DMM’s are easily read, and with their typically high input impedances (>10 for circuits having high resistance. Students learn to read DMM’s quickly and make fewer errors reading values. Reasonable quality DMM’s can be purchased for $60 or less. PASCO strongly recommends the use of DMM’s.

Disadvantages: DMM’s also require the use of a battery, although the lifetime of an alkaline battery in a DMM is quite long. The battery is used on all scales and functions. Most DMM’s give the maximum reading on the selector (i.e., under voltage, “2” means 2-volt maximum, actually 1.99 volt maximum). This may be confusing to some students.

Ω) give good results

VTVM:

The Vacuum Tube Voltmeter or VTVM is a multiple scale, multiple function meter, typically measuring voltage and resistance. They do not usually measure current. The meter is an analog one, with a variety of scales, selected with a rotating switch on the front of the meter.

Advantages: VTVM’s have high input resistances, on

the order of 10

Ω or greater. By measuring the voltage

across a known resistance, current can be measured with a VTVM.

Disadvantages: VTVM’s have multiple scales. Students need practice to avoid the mistake of reading the incorrect one. An internal battery provides the current for measuring resistance, and needs to be replaced from time to time. Grounding problems can occur when using more than one VTVM to make multiple measurements in the same circuit.

Panelmeters:

Individual meters, frequently obtained from scientific supply houses, are available in the form of voltmeters, ammeters, and galvanometers (such as PASCO’s SE-9748 Voltmeter 5 V, 15 V , SE-9746 Ammeter 1 A, 5 A and SE-9749 Galvanometer ± 35 mV). In some models, multiple scales are also available.

Advantages: Meters can be used which have the specific range required in a specific experiment. This helps to overcome student errors in reading.

Disadvantages: Using individual meters leads to errors in choosing the correct one. With limited ranges, students may find themselves needing to use another range and not have a meter of that range available. Many of the individual meters have low input impedances (voltmeters) and large internal resistances (ammeters). Ohmmeters are almost nonexistent in individual form.

Light Bulbs

The #14 bulbs are nominally rated at 2.5 V and 0.3 A. However, due to relatively large variations allowed by the manufacturer, the wattage of the bulbs may vary by 15 to 30%. Therefore, supposedly “identical” bulbs may not shine with equal brightness in simple circuits.

012-05892A AC/DC Electronics Laboratory

Experiment 1: Circuits Experiment Board

EQUIPMENT NEEDED:

– AC/DC Electronics Lab Board: Wire Leads – D-cell Battery – Graph Paper

Purpose

The purpose of this lab is to become familiar with the Circuits Experiment Board, to learn how to construct a complete electrical circuit, and to learn how to represent electrical circuits with circuit diagrams.

Background

➀ Many of the key elements of electrical circuits have been reduced to symbol form. Each symbol

represents an element of the device’s operation, and may have some historical significance. In this lab and the ones which follow, we will use symbols frequently, and it is necessary you learn several of those symbols.

Wire

Switch

Battery (Cell)

Resistor

Light

Fuse

➁ The Circuits Experiment Board has been designed to conduct a wide variety of experiments easily

and quickly. A labeled pictorial diagram of the Experiment Board appears on page 2. Refer to that page whenever you fail to understand a direction which mentions a device on the board itself.

➂ Notes on the Circuits Experiment Board:

a) The springs are soldered to the board to serve as convenient places for connecting wires,

resistors and other components. Some of the springs are connected electrically to devices like the potentiometer and the D-cells.

b) If a spring is too loose, press the coils together firmly to enable it to hold a wire more tightly.

If a spring gets pushed over, light pressure will get it straightened back up. If you find a spring which doesn’t work well for you, please notify your instructor.

c) The components, primarily resistors, are contained in a plastic case at the top of the board.

Keep careful track of the components and return them to the storage bag following each lab period. This way you will get components with consistent values from lab to lab.

d) When you connect a circuit to a D-cell (each “battery” is just a cell, with two or more cells

comprising a battery) note the polarity (+ or -) which is printed on the board. Although in some cases the polarity may not be important, in others it may very important.

e) Due to normal differences between light bulbs, the brightness of “identical” bulbs may vary

substantially.

AC/DC Electronics Laboratory 012-05892A

Procedure

➀ Use two pieces of wire to make connections between the springs on one of the light bulbs to

the springs on the D-cell in such a way that the light will glow. Discuss with your lab partner before you begin actually wiring your circuit which connections you intend to make, and why you think you will be successful in activating the light. If you are not successful, try in order: changing the wiring, using another light, using another cell, asking the instructor for assistance.

a) Sketch the connections that the wires make when you are successful, using the symbols

from the first page of this lab.

b) Re-sketch the total circuit that you have constructed, making the wires run horizontally

and vertically on the page. This is more standard in terms of drawing electrical circuits.

➁ Reverse the two wires at the light. Does this have any

effect on the operation? Reverse the two wires at the cell. Does this have any effect on the operation?

➂ In the following steps, use the pushbutton switch as

shown on the right.

➃ Use additional wires as needed to connect a second

light into the circuit in such a way that it is also lighted. (Use the switch to turn the power on and off once the complete wiring has been achieved.) Discuss your plans with your lab partner before you begin. Once you have achieved success, sketch the connections that you made in the form of a circuit diagram. Annotate your circuit diagram by making appropriate notes to the side indicating what happened with that particular circuit. If you experience lack of success, keep trying.

➤ NOTE: Is your original light the same brightness, or was it brighter or dimmer that it was

during step 1? Can you explain any differences in the brightness, or the fact that it is the same? If not, don’t be too surprised, as this will be the subject of future study.

Battery

–

Switch

Figure 1.1

➄ If you can devise another way of connecting two lights into the same circuit, try it out. Sketch

the circuit diagram when finished and note the relative brightness. Compare your brightness with what you achieved with a single light by itself.

➅ Disconnect the wires and return them to the plastic bag. Replace the equipment to its storage

case.

012-05892A AC/DC Electronics Laboratory

Experiment 2: Lights in Circuits

EQUIPMENT NEEDED:

– AC/DC Electronics Lab Board: Wire Leads – (2) D-cell Batteries – Graph Paper

Purpose

The purpose of this lab is to determine how light bulbs behave in different circuit arrangements. Different ways of connecting two batteries will also be investigated.

Procedure

PART A

➤ NOTE: Due to variations from bulb to bulb, the brightness of one bulb may be substantially

different from the brightness of another bulb in “identical” situations.

➀ Use two pieces of wire to connect a single light bulb to one of the D-cells in such a way that the

light will glow. Include a “switch” to turn the light on and off, preventing it from being on continuously. (You should have completed this step in Experiment 1. If that is the case, review what you did then. If not, continue with this step.)

➁ Use additional wires as needed to connect a second light into the circuit in such a way that it is

also lighted. Discuss your plans with your lab partner before you begin. Once you have achieved success, sketch the connections that you made in the form of a circuit diagram using standard symbols. Annotate your circuit diagram by making appropriate notes to the side indicating what happened with that particular circuit.

➤ NOTE: Is your original light the same brightness, or was it brighter or dimmer than it was

during step 1? Can you explain any differences in the brightness, or why it is the same?

➂ If one of the light bulbs is unscrewed, does the other bulb go out or does it stay on? Why or

why not?

➃ Design a circuit that will allow you to light all three lights, with each one being equally bright.

Draw the circuit diagram once you have been successful. If you could characterize the circuit as being a series or parallel circuit, which would it be? What happens if you unscrew one of the bulbs? Explain.

➄ Design another circuit which will also light all three bulbs, but with the bulbs all being equally

bright, even though they may be brighter or dimmer than in step 4. Try it. When you are successful, draw the circuit diagram. What happens if you unscrew one of the bulbs? Explain.

➅ Devise a circuit which will light two bulbs at the same intensity, but the third at a different

intensity. Try it. When successful, draw the circuit diagram. What happens if you unscrew one of the bulbs? Explain.

➤ NOTE: Are there any generalizations that you can state about different connections to a

set of lights?

AC/DC Electronics Laboratory 012-05892A

PART B

➆ Connect a single D-cell to a single light as in step 1, using a spring clip “switch” to allow

you to easily turn the current on and off. Note the brightness of the light.

⑧ Now connect the second D-cell into the circuit as shown in Figure 2.1a. What is the effect

on the brightness of the light?

Figure 2.1b

Figure 2.1cFigure 2.1a

⑨ Connect the second D-cell as in Figure 2.1b. What is the effect on the brightness? ➉ Finally, connect the second D-cell as in figure 2.1c. What is the effect on the brightness?

➤ NOTE: Determine the nature of the connections between the D-cells you made in steps

8-10. Which of these was most useful in making the light brighter? Which was least useful? Can you determine a reason why each behaved as it did?

PART C

11 Connect the circuit shown in Figure 2.2. What is the effect of rotating the knob on the

device that is identified as a “Potentiometer?”

Discussion

➀ Answer the questions which appear during the experiment procedure. Pay particular

attention to the “NOTED:” questions.

➁ What are the apparent rules for the operation of lights in series? In parallel? ➂ What are the apparent rules for the operation of batteries in series? In parallel? ➃ What is one function of a potentiometer in a circuit?

Battery

–

ABC

Figure 2.2

C W

012-05892A AC/DC Electronics Laboratory

Experiment 3: Ohm’s Law

EQUIPMENT NEEDED:

– AC/DC Electronics Lab Board: Wire Leads – D-cell Battery – Multimeter – Graph Paper

Purpose

The purpose of this lab will be to investigate the three variables involved in a mathematical relationship known as Ohm’s Law.

Procedure

➀ Choose one of the resistors that you have been given. Using the chart on the next page, decode

the resistance value and record that value in the first column of Table 3.1.

➁ MEASURING CURRENT: Construct the circuit shown in Figure 3.1a by pressing the

leads of the resistor into two of the springs in the Experimental Section on the Circuits Experiment Board.

Red (+)

Battery

Figure 3.1a

Black (-)

–

Red (+)

Battery

Black (-)

–

Figure 3.1b

➂ Set the Multimeter to the 200 mA range, noting any special connections needed for measuring

current. Connect the circuit and read the current that is flowing through the resistor. Record this value in the second column of Table 3.1.

➃ Remove the resistor and choose another. Record its resistance value in Table 3.1 then measure

and record the current as in steps 2 and 3. Continue this process until you have completed all of the resistors you have been given. As you have more than one resistor with the same value, keep them in order as you will use them again in the next steps.

➄ MEASURING VOLTAGE: Disconnect the Multimeter and connect a wire from the positive

lead (spring) of the battery directly to the first resistor you used as shown in Figure 3.1b. Change the Multimeter to the 2 VDC scale and connect the leads as shown also in Figure 3.1b. Measure the voltage across the resistor and record it in Table 3.1.

➅ Remove the resistor and choose the next one you used. Record its voltage in Table 3.1 as in step

5. Continue this process until you have completed all of the resistors.

AC/DC Electronics Laboratory 012-05892A

Data Processing

➀ Construct a graph of Current (vertical axis) vs Resistance. ➁ For each of your sets of data, calculate the ratio of Voltage/Resistance. Compare the values

you calculate with the measured values of the current.

Table 3.1

Resistance, Ω Current, amp Voltage, volt Voltage/Resistance

Discussion

➀ From your graph, what is the mathematical relationship between Current and Resistance? ➁ Ohm’s Law states that current is given by the ratio of voltage/resistance. Does your data

concur with this?

➂ What were possible sources of experimental error in this lab? Would you expect each to

make your results larger or to make them smaller?

Reference

Black Brown Red Orange Yellow Green Blue Violet Gray White

0 1 2 3 4 5 6 7 8 9

1st Digit

2nd Digit

No. of Zeros

Tolerance

Fourth Band

None Silver Gold Red

±20% ±10% ±5% ±2%

012-05892A AC/DC Electronics Laboratory

Experiment 4: Resistances in Circuits

EQUIPMENT NEEDED:

– AC/DC Electronics Lab Board: Resistors – Multimeter

Purpose

The purpose of this lab is to begin experimenting with the variables that contribute to the operation of an electrical circuit. This is the first of a three connected labs.

Procedure

➀ Choose three resistors of the same value. Enter those sets of colors in Table 4.1 below. We will

refer to one as #1, another as #2 and the third as #3.

➁ Determine the coded value of your resistors. Enter the value in the column labeled “Coded

Resistance” in Table 4.1. Enter the Tolerance value as indicated by the color of the fourth band under “Tolerance.”

➂ Use the Multimeter to measure the resistance of each of your three resistors. Enter these values

in Table 4.1.

➃ Determine the percentage experimental error of each resistance value and enter it in the appropri-

ate column.

Experimental Error = [(|Measured - Coded|) / Coded ] x 100%.

Table 4.1

1st 2nd 3rd 4th

Colors

Coded

Resistance

Measured

Resistance

Error

Tolerance

➄ Now connect the three resistors into the SERIES CIRCUIT, figure 4.1, using the spring clips on

the Circuits Experiment Board to hold the leads of the resistors together without bending them. Measure the resistances of the combinations as indicated on the diagram by connecting the leads of the Multimeter between the points at the ends of the arrows.

AC/DC Electronics Laboratory 012-05892A

Series

R12=

➤

123

➤

➤ ➤

R23=

123

Figure 4.1

➅ Construct a PARALLEL CIRCUIT, first using combinations of two of the resistors, and then

using all three. Measure and record your values for these circuits.

Parallel

➤ NOTE: Include also R13 by

replacing R2 with R3.

➆ Connect the COMBINATION

CIRCUIT below and measure the various combinations of resistance. Do these follow the rules as you discovered them before?

➤

R12=

R23=

123

Combination

Figure 4.2

R1 =

123

➤

123

2 3

➤ ➤

Figure 4.3

⑧ Choose three resistors having different values. Repeat steps 1 through 7 as above, recording

your data in the spaces on the next page. Note we have called these resistors A, B and C.

012-05892A AC/DC Electronics Laboratory

Table 4.2

Series

Colors

1st 2nd 3rd 4th

➤

Measured

Resistance

Coded

Resistance

➤

ABC

➤ ➤

Error

ABC

Tolerance

Parallel

➤

Figure 4.4

➤

ABC

Figure 4.5

➤ NOTE: Include also R

by replacing RB with RC.

AC/DC Electronics Laboratory 012-05892A

Combination

ABC

➤

ABC

Figure 4.6

➤

Discussion

➀ How does the % error compare to the coded tolerance for your resistors? ➁ What is the apparent rule for combining equal resistances in series circuits? In parallel

circuits? Cite evidence from your data to support your conclusions.

➂ What is the apparent rule for combining unequal resistances in series circuits? In parallel

circuits? Cite evidence from your data to support your conclusions.

➃ What is the apparent rule for the total resistance when resistors are added up in series? In

parallel? Cite evidence from your data to support your conclusions.

Extension

Using the same resistance values as you used before plus any wires needed to help build the circuit, design and test the resistance values for another combination of three resistors. As instructed, build circuits with four and five resistors, testing the basic concepts you discovered in this lab.

Reference

Black Brown Red Orange Yellow Green Blue Violet Gray White

0 1 2 3 4 5 6 7 8 9

1st Digit

2nd Digit

No. of Zeros

Tolerance

None Silver Gold Red

Fourth Band

±20% ±10% ±5% ±2%

Figure 4.7

012-05892A AC/DC Electronics Laboratory

Experiment 5: Voltages in Circuits

EQUIPMENT NEEDED:

– AC/DC Electronics Lab Board: Wire Leads, Resistors – D-cell Battery – Multimeter

Purpose

The purpose of this lab will be to continue experimenting with the variables that contribute to the operation of an electrical circuit. You should have completed Experiment 4 before working on this lab.

Procedure

➀ Connect the three equal resistors that you used in Experiment 4 into the series circuit shown

below, using the springs to hold the leads of the resistors together without bending them. Connect two wires to the D-cell, carefully noting which wire is connected to the negative and which is connected to the positive.

➁ Now use the voltage function on the Multimeter to measure the voltages across the individual

resistors and then across the combinations of resistors. Be careful to observe the polarity of the leads (red is +, black is -). Record your readings below.

Series

➤

Figure 5.1

➤

123

➤

123

AC/DC Electronics Laboratory 012-05892A

➂ Now connect the parallel circuit below, using all three resistors. Measure the voltage across

each of the resistors and the combination, taking care with the polarity as before.

➤ NOTE: Keep all three resistors connected throughout the time you are making your

measurements. Write down your values as indicated below.

Parallel

➤

123

Figure 5.2

➃ Now connect the circuit below and measure the voltages. You can use the resistance read-

ings you took in Experiment 4 for this step.

Combination

123

➤

123

➤

123

Figure 5.3

➄ Use the three unequal resistors that you used in Experiment 4 to construct the circuits shown

below. Make the same voltage measurements that you were asked to make before in steps 1 to 4. Use the same resistors for A, B and C that you used in Experiment 4.

012-05892A AC/DC Electronics Laboratory

Series

ABC

➤

Figure 5.4

➤

Parallel

➤

ABC

➤

ABC

Figure 5.5

AC/DC Electronics Laboratory 012-05892A

Combination

➤

ABC

➤

ABC

Figure 5.6

Discussion

On the basis of the data you recorded on the table with Figure 5.1, what is the pattern for how voltage gets distributed in a series circuit with equal resistances? According to the data you recorded with Figure 5.4, what is the pattern for how voltage gets distributed in a series circuit with unequal resistances? Is there any relationship between the size of the resistance and the size of the resulting voltage?

Utilizing the data from Figure 5.2, what is the pattern for how voltage distributes itself in a parallel circuit for equal resistances? Based on the data from Figure 5.5, what is the pattern for how voltage distributes itself in a parallel circuit for unequal resistances? Is there any relationship between the size of the resistance and the size of the resulting voltage?

Do the voltages in your combination circuits (see Figures 5.3 and 5.6) follow the same rules as they did in your circuits which were purely series or parallel? If not, state the rules you see in operation.

012-05892A AC/DC Electronics Laboratory

Experiment 6: Currents in Circuits

EQUIPMENT NEEDED:

– AC/DC Electronics Lab Board: Resistors and Wire Leads – D-cell Battery – Digital Multimeter

Purpose

The purpose of this lab will be to continue experimenting with the variables that contribute to the operation of electrical circuits.

Procedure

➀ Connect the same three resistors that you used in Experiments 3 and 4 into the series circuit shown

below, using the springs to hold the leads of the resistors together without bending them. Connect two wires to the D-cell, and carefully note which lead is negative and which is positive.

Series

➁ Now change the leads in your DMM so that

they can be used to measure current. You should be using the scale which goes to a maximum of 200 mA. Be careful to observe the polarity of the leads (red is +, black is -). In

order to measure current, the circuit must be interrupted, and the current allowed to flow through the meter. Disconnect the lead wire from the positive terminal of the battery and connect it to the red (+) lead of the meter. Connect the black (-) lead to R originally was connected. Record your reading

, where the wire

in the table as Io. See Figure 6.2.

➂ Now move the DMM to the positions indicated

in Figure 6.3, each time interrupting the circuit,

and carefully measuring the current in each one. Complete the table on the top of the back page.

➤ NOTE: You will be carrying values from Experiments 3 and 4 into the table on the back.

Figure 6.1

Figure 6.2

AC/DC Electronics Laboratory 012-05892A

Figure 6.3

123

➃ Connect the parallel circuit below, using all three resistors. Review the instructions for

connecting the DMM as an ammeter in step 2. Connect it first between the positive terminal of the battery and the parallel circuit junction to measure I0. Then interrupt the various branches of the parallel circuit and measure the individual branch currents. Record your measurements in the table below.

Parallel

123

V2 =

123

Discussion

On the basis of your first set of data, what is the pattern for how current behaves in a series circuit? At this point you should be able to summarize the behavior of all three quantities resistance, voltage and current - in series circuits.

Figure 6.4

On the basis of your second set of data, are there any patterns to the way that currents behave in a parallel circuit? At this time you should be able to write the general characteristics of currents, voltages and resistances in parallel circuits.

012-05892A AC/DC Electronics Laboratory

Experiment 7: Kirchhoff’s Rules

EQUIPMENT NEEDED:

– AC/DC Electronics Lab Board: Resistors, Wire Leads – (2) D-cell Batteries – Digital Multimeter (DMM)

Purpose

The purpose of this lab will be to experimentally demonstrate Kirchhoff’s Rules for electrical circuits.

Procedure

➀ Connect the circuit shown in Figure 7.1a using any of the resistors you have except the 10 Ω

one. Use Figure 7.1b as a reference along with 7.1a as you record your data. Record the

resistance values in the table below. With no current flowing (the battery disconnected), measure the total resistance of the circuit between points A and B.

➁ With the circuit connected to the battery and the current flowing, measure the voltage across

each of the resistors and record the values in the table below. On the circuit diagram in Figure

7.1b, indicate which side of each of the resistors is positive relative to the other end by placing a “+” at that end.

➂ Now measure the

current through each of the resistors. Interrupt the circuit and place the DMM in series to obtain your reading. Make sure you record each of the individual currents, as well as the current flow into or out of the main part of the circuit, I

ABC

Wire

Battery

Figure 7.1a

–

Wire

Figure 7.1b

AC/DC Electronics Laboratory 012-05892A

Table 7.1

Resistance, Ω Voltage, volts Current, mA

Analysis

➀ Determine the net current flow into or out of each of the four “nodes” in the circuit. ➁ Determine the net voltage drop around at least three (3) of the six or so closed loops. Remem-

ber, if the potential goes up, treat the voltage drop as positive (+), while if the potential goes down, treat it as negative (-).

Discussion

Use your experimental results to analyze the circuit you built in terms of Kirchhoff’s Rules. Be specific and state the evidence for your conclusions.

Extension

Build the circuit below and apply the same procedure you used previously. Analyze it in terms of Kirchhoff’s Rules. If possible, try to analyze the circuit ahead of time and compare your measured values with the theoretically computed values.

Figure 7.2

012-05892A AC/DC Electronics Laboratory

Experiment 8: Capacitors in Circuits

EQUIPMENT NEEDED:

– AC/DC Electronics Lab Board: Capacitors, Resistors, Wire Leads – D-cell Battery – Stopwatch or timer with 0.1 sec resolution. – Vacuum Tube Voltmeter (VTVM) or Electrometer (ES-9054B) or Digital Multimeter

(DMM) that has an input impedance of 10 MΩ or greater.

Purpose

The purpose of this lab will be to determine how capacitors behave in R-C circuits. The manner in which capacitors combine will also be studied.

Procedure

➀ Connect the circuit shown in Figure 8.1, using a 100 kΩ resistor and a 100 µF capacitor. Connect

the circuit as shown in Figure 8.1. Connect the VTVM so the black “ground” lead is on the side of the capacitor that connects to the negative terminal of the battery and set it so that it reads to a maximum of 1.5 V DC.

➁ Start with no voltage on the capacitor

and the switch off. If there is remaining voltage on the capacitor, use a piece of

Battery

–

Switch

wire to “short” the two leads together, draining any remaining charge. (Touch the ends of the wire to points B and C as shown in Figure 8.1 to discharge the capacitor.)

➂ Now close the switch by pushing and

holding the button down. Observe the voltage readings on the VTVM, the voltage across the capacitor. How would you describe the manner in which the voltage changes?

Battery

–

Cap

Figure 8.1

Res

➃ If you now open the switch by releasing the button, the capacitor should remain at its present

voltage with a very slow drop over time. This indicates that the charge you placed on the capacitor has no way to move back to neutralize the excess charges on the two plates.

➄ Connect a wire between points A and C in the circuit, allowing the charge to drain back through

the resistor. Observe the voltage readings on the VTVM as the charge flows back. How would you describe the manner in which the voltage falls? (It would be reasonable to sketch a graph showing the manner in which the voltage rose over time as well as the manner in which it fell over time.)

3 VOLTS MAX

C W

➅ Repeat steps 3-5 until you have a good feeling for the process of charging and discharging of a

capacitor through a resistance.

➆ Now repeat steps 3-5, this time recording the time taken to move from 0.0 volts to 0.95 volts while

charging, t your times along with the resistance and capacitance values in Table 8.1 at the top of the back page.

, and the time taken to move from 1.5 volts to 0.55 volts while discharging, tD. Record

AC/DC Electronics Laboratory 012-05892A

Table 8.1

Trial Resistance Capacitance

⑧ Replace the 100 µF capacitor with a 330 µF capacitor. Repeat step 7, recording the charging

and discharging times in Table 8.1. If a third value is available, include it in the data table, too.

⑨ Return to the original 100 µF capacitor, but put a 220 kΩ resistor in the circuit. Repeat step 7,

recording your data in Table 8.1. If a third resistor is provided, use it in the circuit, recording the data.

➤ NOTE:

➀ What is the effect on charging and discharging times if the capacitance is increased? What

mathematical relationship exists between your times and the capacitance?

➁ What is the effect on charging and discharging times if the resistance of the circuit is

increased? What mathematical relationship exists between your times and the resistance?

➉ Return to the original 100 kΩ resistor, but use the 100 µF capacitor in series with the 330 µF

capacitor. Repeat step 7, recording your results in Table 8.2. Now repeat step 7, but with the 100 µF and the 330 µF capacitors in parallel.

R = __________ C

Type of Circuit

Series

Parallel

= __________C2 = __________

Table 8.2

➤ NOTE:What is the effect on the total capacitance if capacitors are combined in series? What

if they are combined in parallel? (Refer to Table 8.2).

012-05892A AC/DC Electronics Laboratory

Experiment 9: Diodes

EQUIPMENT NEEDED:

– AC/DC Electronics Lab Board: 1 KΩ Resistor, 330 Ω Resistor, 1N4007 Diode, Wire Leads – Digital Multimeter (DMM)

– (2) D-cell Batteries

Purpose

The purpose of this lab will be to experimentally determine some of the operating characteristics of semiconductor diodes.

Procedure

Connect the circuit shown in Figure

9.1a using the 1N4007 diode you’ve been supplied and the 1 KΩ resistor . Use Figure 9.1b as a reference along with Figure 9.1a as you record your data. Note the direction that the diode is oriented, with the dark band closer to point B.

Á With the “switch” closed and the

current flowing, adjust the potentiometer until there is a voltage of 0.05 volt between points B and C (V

). Mea-

sure the voltage across the diode (VAB). Record your values in the left-hand side of Table 9.1 under “Forward Bias”.

Â Adjust the potentiometer to attain the

following values for V

0.3,.....2.0 volts. Record the two

voltages for each case.

: 0.1, 0.2,

Battery

–

Switch

–

Res

Figure 9.1a

Diode

Ã Remove the 1 KΩ resistor and replace it with a 330-Ω

resistor. Repeat steps 3 & 4, going from a v oltage of 0.3,

0.4,.....2.0 volts. Record V

andVABin each case.

Ä Reverse the orientation of the diode. Set the diode voltage

) to the values 0.5, 1.0,....3.0 volts. Measure the

resistor voltage (VBC) in each case. Record these values in the columns labeled “Reverse Bias”.

Analysis

Figure 9.1b

À Determine the current flow (I) in each setting by dividing the voltage across the resistor

) by the resistance. Where you switched resistors, be sure to change the divisor.

Á Construct a graph of Current (vertical axis) vs the Voltage across the diode, with the graph

extending into the 2nd quadrant to encompass the negativ e v oltages on the diode.

1N4007

AC/DC Electronics Laboratory 012-05892A

Discussion

Discuss the shape of your graph and what it means for the operation of a semiconductor diode. Did the diode operate the same in steps 3 and 4 as it did in step 5? In steps 3 and 4 the diode was “Forward Biased”, while it was “Reverse Biased” in step 5. Based on your data, what do you think these terms mean? What use might we have for diodes?

Sample Data Table

Diode Type ____________

Forward Bias Reverse Bias

Table 9.1

R, Ω

VAB, volts VBC, volts

I, mA R, Ω

VAB, volts

VBC, volts I, mA

Extensions

➀ If your instructor has a zener diode, carry out the same investigations that you did above. What

differences are there in basic diodes and zener diodes?

➁ Use an LED (light emitting diode) to carry out the same investigations. What differences are

there between basic diodes and LED’s?

012-05892A AC/DC Electronics Laboratory

Experiment 10: Transistors

EQUIPMENT NEEDED:

– AC/DC Electronics Lab Board: 1 kW Resistor, 100 Ω Resistor,

2N3904 Transistor (NPN), Wire Leads – (2) D-cell Batteries – Digital Multimeter (DMM) – Optional: additional Digital Multimeter

Purpose

The purpose of this lab will be to experimentally determine some of the operating characteristics of a transistor.

Procedure

➀ Connect the circuit shown in Figure 10.1a using the 2N3904 Transistor you’ve been supplied. Resistor

= 1 K Ω and resistor R2 = 100 Ω. Use Figure 10.1b as a reference along with Figure 10.1a as you

record your data. Note the leads on the transistor as marked next to the socket in the drawing.

➤ CAUTION: Connecting the transistor incorrectly can destroy the transistor.

Battery

–

2N3904

Battery

–

Figure 10.1a

➁ Adjust the potentiometer carefully until the reading between points A and B is approximately

0.002 volt (2.0 mv). Now read the voltage between points C and D. Record these readings in your data table. Note that V tor, while VCD divided by R2 gives the current flowing in the collector part of the circuit.

divided by R1 gives the current flowing to the base of the transis-

Figure 10.1b

Transistor, top view

Socket

➂ Adjust the potentiometer to give V

corresponding V

: 0.006, 0.010, 0.015, 0.020, 0.025, 0.030, 0.035, 0.040, 0.045, 0.050, 0.055,

the following readings, each time reading and recording the

0.060, 0.080, 0.100, 0.150, 0.200, 0.250 volts. Also set VAB to 0.000 volts.

AC/DC Electronics Laboratory 012-05892A

Analysis

➀ For each of your sets of readings, calculate:

= VAB / R1 and IC = VCD / R

Record all of your current readings in mA.

➁ Plot a graph of I

(vertical axis) vs IB. If you find an area or areas where you need more

points to fill out any curves or sudden changes, simply return to step 2 and make the appropriate measurements.

➂ What is the general shape of the graph? Is there a straight-line region? Does it go through

the origin? Why or why not? Relate the behavior of the transistor at the beginning of the graph to the behavior of the diode in Experiment 9.

➃ What does the leveling off of the graph indicate? Electronics people refer to the transistor as

being “saturated”. How would you describe saturation based on your experiment?

➄ Find the slope of the straight-line region of the graph. This ratio - I

/ IB is referred to as

the current amplification of the transistor. It describes how many times greater changes in the collector current are than the changes in the base current. Report the current amplification of your transistor.

Discussion

Discuss the graph and the calculations you did in the Analysis section.

Sample Data Table

Transistor Type ____________

Table 10.1

R1, Ω VAB, volts IB, mA R2, Ω VCD, volts IC, mA

Extensions

➀ What effect would changing the resistance in the collector circuit (R

the value to 330 Ω or 560 Ω. Does the graph have the same shape? Is the current amplification the same as before? How does the amplification depend on R

) make? Try changing

➁ Obtain a different transistor and repeat the measurements you made in steps 2 & 3. If it is a

PNP transistor, you will need to reverse the wires coming from the D-cells as the emitter needs to be positive, not negative, and the collector will be negative.

012-05892A AC/DC Electronics Laboratory

Experiment 11: Ohm's Law II

EQUIPMENT NEEDED:

– Computer and Science Workshop™ Interface – Power Amplifier (CI-6552A) – AC/DC Electronics Lab Board (EM-8656): 10 Ω resistor, 3 V light bulb, and wire leads – (2) banana plug patch cords (such as SE-9750)

Purpose

The purpose of this experiment is to investigate the relationship between current and voltage in Ohmic and non-Ohmic materials.

Theory

Ohm discovered that when the voltage across a resistor changes, the current through the resistor changes. He expressed this as I = V/R (current is directly proportional to voltage and inversely proportional to resistance). In other words, as the voltage increases, so does the current. The proportionality constant is the value of the resistance. The current is INVERSELY proportional to the resistance. As the resistance increases, the current decreases.

If the voltage across an “Ohmic” resistor is increased, the graph of voltage versus current shows a straight line (if the resistance remains constant). The slope of the line is the value of the resistance. However, if the resistance CHANGES (that is, if the resistor is “non-Ohmic”), the graph of voltage versus current will not be a straight line. Instead, it will show a curve with a changing slope.

For a light bulb, the resistance of the filament will change as it heats up and cools down. At high AC frequencies, the filament doesn’t have time to cool down, so it remains at a nearly constant temperature and the resistance stays relatively constant. At low AC frequencies (e.g., less than one Hertz), the filament has time to change temperature. As a consequence, the resistance of the filament changes dramatically and the resulting change in current through the filament is interesting to watch.

In the first part of this activity, you will investigate a ten ohm (Ω) resistor. In the second part, you will investigate the filament of a small light bulb.

PROCEDURE

Part A – Ten Ohm Resistor

PART I: Computer Setup

➀ Connect the Science Workshop interface to the computer, turn on the interface, and turn on the

computer.

➁ Plug the Power Amplifier into Analog Channel A. Plug the power cord into the back of the

Power Amplifier and connect the power cord to an appropriate electrical receptacle

AC/DC Electronics Laboratory 012-05892A

➂ In the Physics Folder of the Science Workshop Experiment Library, open the document:

Macintosh: “P46 Ohm's Law” / Windows: “P46_OHM.SWS”

The document opens with a Scope (oscilloscope) display of Voltage (V) versus Current (A), and the Signal Generator window which controls the Power Amplifier.

➤ NOTE: For quick reference, see the Experiment Notes window. To bring a display to the top,

click on its window or select the name of the display from the list at the end of the Display menu. Change the Experiment Setup window by clicking on the “Zoom” box or the Restore button in the upper right hand corner of that window.

➃ The “Sampling Options…” for this experiment are: Periodic Samples = Fast at 4000 Hz (set in the

Scope display using the Sweep Speed control).

012-05892A AC/DC Electronics Laboratory

➄ The Signal Generator is set to output 3.00 V, triangle AC waveform, at 60.00 Hz.

➅ The Scope is set to show Output Voltage on the vertical axis at 1.000 v/div and Current (Analog

A) on the horizontal axis at 0.100 v/div.

➆ Arrange the Scope display and the Signal Generator window so you can see both of them.

PART II: Sensor Calibration and Equipment Setup

• You do not need to calibrate the Power Amplifier.

➀ Place a ten ohm (Ω) resistor in the pair of component springs

KIT NO.

nearest to the banana jacks at the lower right corner of the AC/DC Electronics Lab Board.

➁ Connect banana plug patch cords from the output of the

Power Amplifier to the banana jacks on the AC/DC Electronics Lab Board.

➂ Turn on the power switch on the back of the Power Amplifier.

3 VOLTS MAX

C W

Part III: Data Recording – Resistor (10 Ω)

➀ Click the “ON” button ( ) in the Signal Generator

window.

➁ Click the “MON” button ( ) in the Experiment Setup

window to start monitoring data. Observe the Scope display of Voltage and Current. Wait a few seconds, then click the

“STOP” button (

AC/DC ELECTRONICS LABORATORY

➂ Click the “OFF” button ( ) in the Signal Generator window. Turn off the power switch on

to Power Amp.

10Ω

(brown, black, black)

the back of the Power Amplifier.

AC/DC Electronics Laboratory 012-05892A

➃ Select the Scope display.

Analyzing the Data – Resistor (10 Ω)

➀ Click the “Smart Cursor” button ( ) in the Scope. The cursor changes to a cross-hair. Move

the cursor into the display area of the Scope.

• The Y-coordinate of the cursor/cross-hair is shown next to the Vertical Axis Input button:

• The X-coordinate of the cursor/cross-hair is shown next to the Horizontal Axis Input button:

➁ Use the coordinates of a point on the trace on the Scope display to determine the slope of the trace

on the Scope. Record the value of the slope.

012-05892A AC/DC Electronics Laboratory

slope (10 Ω) = ________ Volts/Amps

Optional

➀ Replace the 10 Ω resistor with the 100 Ω resistor. ➁ Click the “Increase Sweep Speed” button ( ) in the Scope display to change the sensitivity

of the horizontal axis to 0.010 v/div.

➂ Repeat the experiment. Record the new slope.

slope (100 Ω) = ________ Volts/Amps

Part B – Light Bulb Filament

PART I: Computer Setup for Light Bulb Filament

For this part of the activity you will use the filament of a light bulb as the resistor. In the Computer Setup you will change the Amplitude and Frequency of the output AC waveform. You will also change some of the settings on the Scope display.

➀ Click the Signal Generator window to make it active.

➁ Click on the Amplitude value to highlight it. Type in “2.5” as the new value. Press the “enter” key.

AC/DC Electronics Laboratory 012-05892A

➂ Click on the Frequency value to highlight it. Type in “0.30” as the new value. Press the “enter” key.

➃ Click the Scope display to make it active.

• You will change the rate at which the scope is sampling data.

➄ Click the “Horizontal Input” button. Use the Horizontal Input menu to select “Time Input” (at the

bottom of the list).

Horizontal Input button Horizontal Input menu

➅ Repeatedly click the “Decrease Sweep Speed” button ( ) until the Sweep Speed is 500.00

ms/div.

➄ Click the “Horizontal Input” button again. Use the Horizontal Input menu to select “Analog A” (at

the top of the list).

Horizontal Input button Horizontal Input menu

• After making changes, the Scope display should be similar to the figure below:

012-05892A AC/DC Electronics Laboratory

PART II: Equipment Setup for Light Bulb Filament

➀ Remove the resistor from the component springs on the AC/DC Electronics Lab Board. ➁ Use two of the 10” wire leads to connect between the component springs near the banana jacks

and the component springs above and below 3 VOLT BULB “C”.

KIT NO.

3.3Ω

3 VOLTS MAX

EM-8656

AC/DC ELECTRONICS LABORATORY

C W

PART III: Data Recording – Light Bulb Filament

AC/DC Electronics Laboratory 012-05892A

➀ Turn on the switch on the back of the Power Amplifier. ➁ Click the “ON” button in the Signal Generator window. ➂ Click the “MON” button in the Experiment Setup window to begin monitoring data. Observe the

Scope display of Voltage versus Current for the light bulb filament.

➃ Wait a few seconds, then click the “STOP” button. ➄ Click the “OFF” button in the Signal Generator window. Turn off the power switch on the back of

the Power Amplifier.

Questions

➀ Compare the slope of the 10 Ω resistor as shown in the Scope to the “official” value of resistance.

In other words, how close is the value of slope to the value of resistance?

➁ Why does the slope of the light bulb trace change? ➂ Does the resistor have a constant resistance? Does the light bulb? Why or why not? ➃ The slope of the graph for the light bulb is not symmetric. Why is the slope of the current trace

different when the filament is heating up compared to the trace of current when the filament is cooling down?

012-05892A AC/DC Electronics Laboratory

Experiment 12: RC Circuit

EQUIPMENT NEEDED:

– Computer and Science Workshop™ Interface – Power Amplifier (CI-6552A) – Voltage Sensor (CI-6503) – AC/DC Electronics Lab Board (EM-8656): 100 Ω resistor and 330 µF capacitor – (2) banana plug patch cords (such as SE-9750) – LRC meter (optional)

Purpose

The purpose of this experiment is to investigate how the voltage across a capacitor varies as it charges and to find the capacitive time constant.

Theory

When an uncharged capacitor is connected across a DC voltage source, the rate at which it charges up decreases as time passes. At first, the capacitor is easy to charge because there is very little charge on the plates. But as charge accumulates on the plates, the voltage source must “do more work” to move additional charges onto the plates because the plates already have charge of the same sign on them. As a result, the capacitor charges exponentially, quickly at the beginning and more slowly as the capacitor becomes fully charged. The charge on the plates at any time is given by:

−t

q=qo1−e

()

where qo is the maximum charge on the plates and τ is the capacitive time constant (τ = RC, where R is resistance and C is capacitance).

➤ NOTE: The stated value of a capacitor may vary by as much as ±20% from the actual value.

Taking the extreme limits, notice that when t = 0, q = 0 which means there is not any charge on the plates initially. Also notice that when t goes to infinity, q goes to q

which means it

takes an infinite amount of time to completely charge the capacitor.

The time it takes to charge the capacitor to half full is called the half-life and is related to the time constant in the following way:

=τ ln2

In this experiment the charge on the capacitor will be measured indirectly by measuring the voltage across the capacitor since these two values are proportional to each other: q = CV.

AC/DC Electronics Laboratory 012-05892A

Procedure

PART I: Computer Setup

➀ Connect the Science Workshop interface to the computer, turn on the interface, and turn on the

computer.

➁ Connect the Voltage Sensor to Analog Channel A. Connect the Power Amplifier to Analog

Channel B. Plug the power cord into the back of the Power Amplifier and connect the power cord to an appropriate electrical receptacle

➂ In the Physics Folder of the Science Workshop Experiment Library, open the document:

Macintosh: “P49 RC Circuit” / Windows: “P49_RCCI.SWS”

The document opens with a Graph display of Voltage (V) versus Time (sec), and the Signal Generator window which controls the Power Amplifier.

012-05892A AC/DC Electronics Laboratory

➤ Note: For quick reference, see the Experiment Notes window. To bring a display to the top,

➃ The “Sampling Options…” for this experiment are: Periodic Samples = Fast at 1000 Hz and

Stop Condition = 4.00 seconds.

➄ The Signal Generator is set to output 4.00 V, “positive only” square AC Waveform, at 0.40 Hz.

The “ON/OFF” button is set to “Auto” so the Signal Generator will start automatically when you click MON (Monitor) or REC (Record) and stop automatically when you click STOP or PAUSE.

➅ The Graph is scaled between 0 and 5 V on the vertical axis (Voltage), and 0 to 4 seconds on the

horizontal axis (Time).

PART II: Sensor Calibration and Equipment Setup

• You do not need to calibrate the Voltage Sensor or the Power Amplifier.

➀ Place a 100 ohm (Ω) resistor (brown, black, brown) in the pair

of component springs nearest to the top banana jack at the lower right corner of the AC/DC Electronics Lab Board.

Ω

KIT NO.

➁ Connect a 330 microfarad (µF) capacitor between the compo-

nent spring on the left end of the 100 Ω resistor and the component spring closest to the bottom banana jack.

➂ Put alligator clips on the Voltage Sensor banana plugs. Connect the

3 VOLTS MAX

C W

alligator clips to the wires at both ends of the 330 µF capacitor.

➃ Connect banana plug patch cords from the output of the Power

Amplifier to the banana jacks on the AC/DC Electronics Lab Board.

300 µF Cap

Part III: Data Recording

➀ Turn on the power switch on the back of the Power Amplifier.

AC/DC ELECTRONICS LABORATORY

➁ Click the “REC” button ( ) in the Experiment Setup

100 Ω Res

to Power Amp.

window to start recording data. The power amplifier output will automatically start when data recording begins..

➂ Data recording will continue for four seconds and then stop automatically.

• Run #1 will appear in the Data list in the Experiment Setup window.

AC/DC Electronics Laboratory 012-05892A

➃ When data recording is complete, turn off the switch on the back of the Power Amplifier.

Analyzing the Data

➀ Click the “Autoscale” button ( ) in the Graph to rescale the Graph to fit the data.

➁ Click the “Magnifier” button ( ). Use the cursor to click-and-draw a rectangle over a region

of the plot of Voltage versus Time that shows the voltage rising from zero volts to the maximum volts.

• This will give you an expanded view of the Voltage versus Time plot for that region.

012-05892A AC/DC Electronics Laboratory

➂ Click the “Smart Cursor” button ( ). The cursor changes to a cross-hair when you move the

cursor into the display area of the Graph.

• The Y-coordinate of the cursor/cross-hair is shown next to the vertical axis.

• The X-coordinate of the cursor/cross-hair is shown next to the horizontal axis.

➃ Move the cursor to the point on the plot where the voltage begins to rise. Record the time that is

shown in the area below the horizontal axis.

➄ Move the “Smart Cursor” to the point where the voltage is approximately 2.00 Volts. Record the

new time that is shown in the area below the horizontal axis.

➅ Find the difference between the two times and record it as the time to “half-max”, or t

Data

Beginning time = _________ s

Time to 2.00 V = _________ s

Time to half-max (t

➀ Use

=τ ln2

) = __________ s

1/2

= 0.693 RC to calculate the capacitance (C) of the capacitor.

Capacitance = _________ Farad

➁ If a capacitance meter is available, use it to measure the capacitance of the capacitor. Using the

Percent Difference method, compare the measured value to the experimental value. (Remember, the stated value of a capacitor may vary by as much as ±20% from the actual measured value.) If a capacitance meter is not available, use the Percent Difference method and compare the stated value (e.g., 330 µF) to the experimental value.

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AC/DC Electronics Laboratory 012-05892A

Questions

➀ The time to half-maximum voltage is how long it takes the capacitor to charge halfway. Based on

your experimental results, how long does it take for the capacitor to charge to 75% of its maximum?

➁ After four “half-lifes” (i.e., time to half-max), to what percentage of the maximum charge is the

capacitor charged?

➂ What is the maximum charge for the capacitor in this experiment? ➃ What are some factors that could account for the percent difference between the stated and

experimental values?

012-05892A AC/DC Electronics Laboratory

Experiment 13: LR Circuit

EQUIPMENT NEEDED:

– Computer and Science Workshop™ Interface – Power Amplifier (CI-6552A) – (2) Voltage Sensor (CI-6503) – AC/DC Electronics Lab Board (EM-8656): inductor coil & core, 10 Ω resistor, wire leads – Multimeter – (2) banana plug patch cords (such as SE-9750) – LCR (inductance-capacitance-resistance) meter (optional)

Purpose

This experiment displays the voltages across the inductor and resistor in an inductor-resistor circuit (LR circuit), and the current through the inductor so that the behavior of an inductor in a DC circuit can be studied.

Theory

When a DC voltage is applied to an inductor and a resistor in series a steady current will be established:

) = I

VR= IR

−

(1 − e

max

is the inductive time constant. The inductive

, the voltage across the resistor is estab-

)

max

where Vo is the applied voltage and R is the total resistance in the circuit. But it takes time to establish this steady-state current because the inductor creates a back-emf in response to the rise in current. The current will rise exponentially:

(

I = I

where L is the inductance and the quantity time constant is a measure of how long it takes the current to be established. One inductive time

constant is the time it takes for the current to rise to 63% of its maximum value (or fall to 37% of its maximum). The time for the current to rise or fall to half its maximum is related to the inductive time constant by

Since the voltage across a resistor is given by lished exponentially:

max

(1 − e

=τ(ln 2)

−t

VR= Vo(1 − e

)

AC/DC Electronics Laboratory 012-05892A

Since the voltage across an inductor is given by

VL= L



, the voltage across the inductor



starts at its maximum and then decreases exponentially:

−(

)

VL= Voe

After a time t >> t, a steady-state current I equal to the applied voltage, Vo. The voltage across the inductor is zero. If, after the maximum current is established, the voltage source is turned off, the current will then decrease exponentially to zero while the voltage across the resistor does the same and the inductor again produces a back emf which decreases exponentially to zero. In summary:

DC Voltage applied: DC Voltage turned off:

I = I

max

VR= Vo1−e

VL= Voe

At any time, Kirchhoff’s Loop Rule applies: The algebraic sum of all the voltages around the series circuit is zero. In other words, the voltage across the resistor plus the voltage across the inductor will add up to the source voltage.

−(

1−e

()

−(

()

−(

Procedure

PART I: Computer Setup

is established and the voltage across the resistor is

max

)

I = I

VR= Voe

VL= V01–e

max

−(

–(t/τ)

)

➀ Connect the Science Workshop interface to the computer, turn on the interface, and turn on the

computer.

➁ Connect one Voltage Sensor to Analog Channel A. This sensor will be “Voltage Sensor A”.

Connect the second Voltage Sensor to Analog Channel B. This sensor will be “Voltage Sensor B”.

➂ Connect the Power Amplifier to Analog Channel C. Plug the power cord into the back of the

Power Amplifier and connect the power cord to an appropriate electrical receptacle

➃ In the Physics Folder of the Science Workshop Experiment Library, open the document:

Macintosh: “P50 LR Circuit” / Windows: “P50_LRCI.SWS”

012-05892A AC/DC Electronics Laboratory

The document opens with a Graph display of Voltage (V) versus Time (sec), and the Signal Generator window which controls the Power Amplifier.

➤ NOTE: For quick reference, see the Experiment Notes window. To bring a display to the top,

➄ The “Sampling Options…” for this experiment are: Periodic Samples = Fast at 10000 Hz, Start

Condition when Analog C voltage goes to 0 Volts, and Stop Condition = Time at 0.02 seconds.

➅ The Signal Generator is set to output 3.00 V, square AC waveform, at 50.00 Hz.

➅ Arrange the Graph display and the Signal Generator window so you can see both of them.

PART II: Sensor Calibration and Equipment Setup

• You do not need to calibrate the Power Amplifier, or the Voltage sensors.

➀ Connect a 5 inch wire lead between a component spring next to the top banana jack, and the

component spring at the right hand edge of the inductor coil.

AC/DC Electronics Laboratory 012-05892A

➁ Connect the 10 Ω resistor (brown, black, black)

between the component spring at the left hand edge of the inductor coil, and the second component spring to the left of the top banana jack.

➂ Connect another 5 inch wire lead between the

component spring nearest to the one in which one end of the 10 Ω resistor is connected, and a component spring nearest to the bottom banana jack at the lower right corner of the AC/DC Electronics Lab Board.

➃ Put alligator clips on the banana plugs of both

Voltage Sensors. Connect the alligator clips of Voltage Sensor “A” to the component springs at both sides of the inductor coil.

➄ Connect the alligator clips of Voltage Sensor “B” to

the wires at both ends of the 10 resistor.

➅ Connect banana plug patch cords from the output of

the Power Amplifier to the banana jacks on the AC/ DC Electronics Lab Board.

to Channel A

KIT NO.

3Ω

3 VOLTS MAX

10 Ω Res

AC/DC ELECTRONICS LABORATORY

to Power Amp.

Part III: Data Recording

➀ Use the multimeter to measure the resistance of the

inductor coil. Record the resistance in the Data Table.

to Channel B

➁ Use the multimeter to check the resistance of the 10 Ω resistor. Record the resistance in the Data

Table.

➂ Turn on the power switch on the back of the Power Amplifier. ➃ Click the “ON” button ( ) in the Signal Generator window. The power amplifier output will

begin.

➄ Click the “REC” button ( ) to begin data recording.

• Data recording will end automatically after 0.02 seconds. Run #1 will appear in the Data list in the Experiment Setup window.

➅ Click the “OFF” button ( ) in the Signal Generator window. Turn off the power switch on the

back of the Power Amplifier.

Analyzing the Data

• The voltage across the resistor is in phase with the current. The voltage is also proportional to the current (that is, V = IR). Therefore, the behavior of the current is studied indirectly by studying the behavior of the voltage across the resistor (measured on Analog Channel B).

012-05892A AC/DC Electronics Laboratory

➀ Click the “Smart Cursor” button ( ) in the Scope. The cursor changes to a cross-hair. Move

the cursor into the display area of the Scope.

• The Y-coordinate of the cursor/cross-hair is shown next to the Vertical Axis.

• The X-coordinate of the cursor/cross-hair is shown next to the Horizontal Axis.

➁ Move the cursor/cross-hair to the top of the exponential part of the curve when the plot of

voltage across the resistor (Analog Channel B) is at its maximum. Record the peak voltage (Ycoordinate) and the time (X-coordinate) for that point in the Data Table. Determine the voltage that is half of the peak (the half-max voltage).

Y-coordinate

Smart

Cursor

X-coordinate

➂ Move the cursor down the exponential part of the plot of resistor voltage until half the maximum

(peak) voltage is reached. Record the X-coordinate (time) for this point.

Smart

Cursor

X-coordinate

AC/DC Electronics Laboratory 012-05892A

➃ Subtract the time for the peak voltage from the time for the half-max voltage to get the time for the

voltage to reach half-max. Record this time in the Data Table.

➄ Based on the total resistance in the circuit and the stated value for the inductance of the inductor

coil (8.2 millihenry or 0.0082 mH), calculate

Data Table

Inductor Resistance Ω Resistor Resistance Ω Peak Voltage (for Resistor) V Time at Peak Voltage sec Time at Half-Maximum Voltage sec Time to reach Half-Maximum sec τ = L/R

Questions

➀ How does the inductive time constant found in this experiment compare to the theoretical value

given by t = L/R? (Remember that R is the total resistance of the circuit and therefore must include the resistance of the coil as well as the resistance of the resistor.)

➀ Does Kirchhoff’s Loop Rule hold at all times? Use the graphs to check it for at least three different

times: Does the sum of the voltages across the resistor and the inductor equal the source voltage at any given time?

Extension

Place the iron core in the coil and repeat “Part III: Data Recording”. From the relationship and t

= τ ln(2) find the new value of the inductor.

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012-05892A AC/DC Electronics Laboratory

Experiment 14: LRC Circuit

EQUIPMENT NEEDED:

– Computer and Science Workshop™ Interface – Power Amplifier (CI-6552A) – Voltage Sensor (CI-6503) – AC/DC Electronics Lab Board (EM-8656): inductor coil & core, 10 Ω resistor,

100 µF capacitor, wire lead

– LCR (inductance-capacitance-resistance) meter (SB-9754) – (2) banana plug patch cords (such as SE-9750) – graph paper

Purpose

The purpose of this experiment is to study resonance in an inductor-resistor-capacitor circuit (LRC circuit) by examining the current through the circuit as a function of the frequency of the applied voltage.

Theory

The amplitude of the AC current (Io) in a series LRC circuit is dependent on the amplitude of the applied voltage (Vo) and the impedance (Z).

Io=

Since the impedance depends on frequency, the current varies with frequency:

Z = XL− X

()

where XL = inductive reactance = ωL, XC = capacitive reactance = angular frequency = 2πν (ν = linear frequency). The current will be maximum when the circuit

is driven at its resonant frequency:

res

One can show that, at resonance, XL = XC at resonance and thus the impedance (Z) is equal to R. So at resonance the impedance is the lowest value possible and the current will be the largest possible.

+ R

, R = resistance, and ω =

In this experiment the amplitude of the current vs. frequency is plotted. Since the current is a maximum at the resonant frequency and is less for higher or lower frequencies, the graph is expected to peak at the resonant frequency.

AC/DC Electronics Laboratory 012-05892A

Procedure

PART I: Computer Setup

➀ Connect the Science Workshop interface to the computer, turn on the interface, and turn on the

computer.

➁ Connect the Power Amplifier to Analog Channel A. Plug the power cord into the back of the

Power Amplifier and connect the power cord to an appropriate electrical receptacle.

➂ Connect the Voltage Sensor to Analog Channel B. The voltage measured at Analog Channel B

will be used to calculate the current, I, which is related to the voltage across the resistor by

I =

➃ In the Physics Folder of the Science Workshop Experiment Library, open the document:

Macintosh: “P51 LRC Circuit” / Windows: “P51_LRCC.SWS”

The document opens with a Scope (oscilloscope) display of Voltage (V) versus Time (msec), and the Signal Generator window which controls the Power Amplifier.

012-05892A AC/DC Electronics Laboratory

➤ NOTE: For quick reference, see the Experiment Notes window. To bring a display to the top,

➃ The Signal Generator is set to output 3.00 V, sine AC waveform, at 10.00 Hz. The “ON/OFF”

button is set to “Auto” so the Signal Generator will start automatically when you click MON (Monitor) or REC (Record) and stop automatically when you click STOP or PAUSE.

➄ Arrange the Scope display and the Signal Generator window so you can see both of them.

PART II: Sensor Calibration and Equipment Setup

• You do not need to calibrate the Power Amplifier.

➀ Connect a 5 inch wire lead between a component spring next to the top banana jack, and the

component spring at the right hand edge of the inductor coil.

➁ Connect the 10 Ω resistor (brown, black, black)

between the component spring at the left hand edge of the inductor coil, and the second component spring to the left of the top banana jack.

3Ω

KIT NO.

➂ Connect the 100 µF capacitor between the compo-

nent spring nearest to the one in which one end of the 10 Ω resistor is connected, and a component spring nearest to the bottom banana jack at the

3 VOLTS MAX

lower right corner of the AC/DC Electronics Lab Board.

➃ Put alligator clips on the banana plugs of the

Voltage Sensor. Connect the alligator clips of the Voltage Sensor to the wires at both ends of the 10 Ω resistor.

➄ Connect banana plug patch cords from the output

of the Power Amplifier to the banana jacks on the AC/DC Electronics Lab Board.

100 µF

Cap

10 Ω Res

to Power Amp.

AC/DC ELECTRONICS LABORATORY

to Channel B

AC/DC Electronics Laboratory 012-05892A

Part III: Data Recording

➀ Turn on the power switch on the back of the power amplifier.

➁ Click the “MON” button ( ) to begin data monitoring. Record the value of the frequency in

the Data Table.

• Use the Smart Cursor in the Scope to measure the source voltage and the resistor voltage. To find the resonant frequency of the LRC circuit, adjust the frequency in the Signal Generator window until the voltage across the resistor increases to a maximum value.

➂ To measure the output voltage, click the “Smart Cursor” button ( ) in the Scope display. The

cursor changes to a cross-hair. Move the cursor/cross-hair to a peak of the output voltage, V

(trace for Channel A). Record the voltage that is displayed next the Input menu button.

➃ To measure the voltage across the resistor, move the cursor/cross-hair to a peak of the voltage

across the resistor, V

(trace for Channel B). Record the voltage.

➄ In the Signal Generator window, click on the Up arrow ( ) to increase the frequency by 10 Hz.

Record the new frequency in the Data Table. Repeat the process of using the Smart Cursor to find the new voltages for the output, V

, and the resistor, VR.

➅ Repeat the process until 150 Hz is reached. As the frequency is increased, adjust the sweep speed

in the Scope display using the “Increase Speed” button ( ) as needed.

➆ Look at the Data Table and determine approximately the resonant frequency (where voltage

across the resistor reaches a maximum).

➇ Click on the frequency in the Signal Generator window to highlight it. Type in the approximate

resonant frequency, then press “enter”.

012-05892A AC/DC Electronics Laboratory

➈ Make fine adjustments to the frequency until the trace of voltage from Channel B is in phase

with the trace of Output Voltage. You can adjust the frequency by clicking the “Up” or “Down” Frequency arrows while pressing the following modifier keys:

To adjust the frequency Press this key while clicking

1 Hz Control

0.1 Hz Option

0.01 Hz Command or ALT

➉ To check whether the trace of voltage from Channel B is in phase with the trace of Output

Voltage, switch the Scope display to “X-Y” mode:

a. Click the “STOP” button (

). Click the Horizontal Axis Input menu button ( ).

Select “Analog B” from the Horizontal Axis Input menu.

b. Click the Channel B Input menu button (

“No Input” from the Channel B Input menu.

) along the right edge of the Scope. Select

AC/DC Electronics Laboratory 012-05892A

c. Click the “MON” button to begin monitoring data again. Adjust the frequency in the Signal

Generator window as needed to reach the resonant frequency. Record the resonant frequency.

• When the two inputs are in phase, the Scope display in “X-Y” mode will show a diagonal line. Any phase difference will cause an oval trace.

• XY mode at 40 Hz • XY mode at resonant frequency

Click the “STOP” button. Turn off the switch on the back of the power amplifier.

Use the LCR meter to measure the inductance of the inductor coil with core, and the capacitance

of the 100 µF capacitor. Record these values in the Data Table.

Analyzing the Data

➀ Graph the current (or voltage across the resistor divided by output voltage: V

linear frequency on separate graph paper. (NOTE: The frequency in the Signal Generator window is the linear frequency.)

R/Vo

➁ Using the resonant frequency found from the Scope display, calculate the resonant angular

freqeuncy and record the value in the Data Table:

= 2

πν

res

➂ Calculate the theoretical resonant angular frequency using the following:

res

) versus the

012-05892A AC/DC Electronics Laboratory

Data Table

Freq(Hz) V

10 90

20 100

30 110

40 120

50 130

60 140

70 150

Item Value

Resonant frequency Hz

Resonant angular frequency Hz

Inductance mH

Capacitance µF

Theoretical resonant angular frequency Hz

Questions

➀ How does your measured value for resonant angular frequency compare to the theoretical value

for resonant angular frequency?

Remember,

Percent difference =

theoretical − actual

x100%

theoretical

➁ Is the plot of current (V

Explain.

) versus frequency symmetrical about the resonant frequency?

R/Vo

➂ At resonance, the reactances of the inductor and the capacitor cancel each other so that the

impedance (Z) is equal to just the resistance (R). Calculate the resistance of the circuit by using

the amplitude of the current at resonance in the equation the applied voltage). Is this resistance equal to 10 Ω? Why not?

(where V is the amplitude of

AC/DC Electronics Laboratory 012-05892A

Optional

➀ Use the voltage sensor in Analog Channel B to measure the peak voltage across each of the

components of the circuit individually. The sum of these peak voltages do not equal the applied peak voltage. Why not? Draw a phasor diagram to explain this.

➁ Determine whether the resonant frequency depends on the resistance.

To see if the resistance makes a difference, set the Scope to the resonant frequency and then replace the 10 Ω resistor by a 100 Ω resistor. Does the resonant frequency increase, decrease, or stay the same?

012-05892A AC/DC Electronics Laboratory

Experiment 15: Diode Lab – Part 1

EQUIPMENT NEEDED:

– Computer and Science Workshop™ Interface – Power Amplifier (CI-6552A) – (2) Voltage Sensor (CI-6503) – AC/DC Electronics Lab Board (EM-8656) – (2) Banana plug patch cords (such as SE-9750)

Purpose

In this experiment, the properties of various type of diodes are investigated.

Theory

A diode (or p-n junction rectifier) is an electronic device which only allows current to flow in one direction through it once a certain forward voltage is established across it. If the voltage is too low, no current flows through the diode. If the voltage is reversed, no current flows through the diode (except for a very small reverse current).

A light-emitting diode emits light as current passes through the diode in the forward direction. A red-green diode is actually two diodes connected together antiparallel so that the red diode allows current to flow in one direction and the green diode allows current to flow in the opposite direction. Thus, if DC (direct current) is applied to the red-green diode, it will be only red or only green depending on the polarity of the applied DC voltage. But if AC (alternating current) is applied to the red-green diode (bicolor LED), the diode will repeatedly blink red then green as the current repeatedly changes direction.

A bicolor LED is an example of a Zener diode. A Zener diode allows current to flow in one direction when the forward voltage is large enough, and it allows current to flow in the opposite direction when volts).

Overview

There are several units to the Diode Lab. You will complete the first two units in Part 1 (this experiment). You will complete Unit Three and Unit Four in Part 2 (the next experiment).

reverse voltage (called the “breakdown” voltage) is large enough (usually a few

Unit Activity

One diode properties Two LED’s and Zener diode Three rectify a sine wave Four basic power supply

In the first unit you will investigate the general properties of a diode. In the second unit you will investigate different types of diodes, including light-emitting diodes (LED’s) and a Zener diode. In the third unit you will rectify a sine wave generated by the Power Amplifier. In the last unit you will setup the basic circuitry for a power supply.

AC/DC Electronics Laboratory 012-05892A

PROCEDURE: Unit One – Diode Properties

PART I: Computer Setup

➀ Connect the Science Workshop interface to the computer, turn on the interface, and turn on the

computer.

➁ Connect one Voltage Sensor to Analog Channel A. Connect the second Voltage Sensor to Analog

Channel B.

➂ Connect the Power Amplifier to Analog Channel C. Plug the power cord into the back of the

Power Amplifier and connect the power cord to an appropriate electrical receptacle.

➃ In the Physics Folder of the Science Workshop Experiment Library, open the document:

Macintosh: “P52 Diodes” / Windows: “P52_DIOD.SWS”

The document opens with a Graph display of Current in milliamperes (mA) versus Voltage (V), and the Signal Generator window which controls the Power Amplifier. The Current is a calculation based on the voltage drop across a 1000 ohm resistor (as measured on Channel B).

012-05892A AC/DC Electronics Laboratory

➤ NOTE: For quick reference, see the Experiment Notes window. To bring a display to the top,

➄ The Signal Generator is set to output 6.00 V, up-ramp AC waveform, at 2.00 Hz.

➅ The “Sampling Options…” are: Periodic Samples = Fast at 500 Hz, Start condition when Analog

Output = -5.9 V, and Stop condition when Samples = 250.

➆ Arrange the Graph display and the Signal Generator window so you can see both of them.

PART II: Sensor Calibration and Equipment Setup

• You do not need to calibrate the Voltage Sensors or Power Amplifier.

➀ Connect the 1N-4007 diode (black with gray stripe

at one end) between the component spring next to the top banana jack and the component spring to the left of the banana jack. Arrange the diode so the gray stripe is at the left end.

➁ Connect the 1 k Ω resistor (brown, black, red)

between the component spring next to the bottom banana jack and the component spring to the left of the bottom banana jack.

➂ Connect a 5 inch wire lead between the component

spring at the left end of the diode and the component spring at the left end of the 1 kΩ resistor.

channel A channel B

black black

black

red red

Diode

1000 Ω

Power Amplifier

red

EM-8656

to Channel A

KIT NO.

3.3Ω

3 VOLTS MAX

C W

Diode

Res

AC/DC ELECTRONICS LABORATORY

to Power Amp

➃ Put alligator clips on the banana plugs of both

voltage sensors. Connect the alligator clips of the Channel A voltage sensor to the wires at both ends of the diode.

to Channel B

AC/DC Electronics Laboratory 012-05892A

➄ Connect the alligator clips of the Channel B voltage sensor to the wires at both ends of the 1 k

resistor.

➅ Connect banana plug patch cords from the output of the Power Amplifier to the banana jacks on

the AC/DC Electronics Lab Board.

Part III: Data Recording - Diode and 1 k Resistor

➀ Turn on the power switch on the back of the power amplifier. ➁ Click the “ON” button ( ) in the Signal Generator window.

➂ Click the “REC” button ( ) to begin data recording.

• Data recording will end automatically after 250 samples are measured. Run #1 will appear in the Data list in the Experiment Setup window.

➃ Click the “OFF” button ( ) in the Signal Generator window. Turn off the switch on the back

of the power amplifier.

ANALYZING THE DATA: Diode and 1 kΩ Resistor

➀ Click the “Autoscale” button ( ) to resize the Graph to fit the data.

• The vertical axis shows Current in milliamps based on a calculation using the voltage drop across the 1 kΩ resistor. The horizontal axis shows Voltage across the diode.

➁ Select “Save As…” from the File menu to save your data. Select “Print Active Display” from the

File menu to print the Graph.

➂ Click the “Magnifier” button ( ). The cursor changes to a magnifying glass shape.

012-05892A AC/DC Electronics Laboratory

➃ Use the cursor to click-and-draw a rectangle around the region of the plot of current and voltage

where the current begins to increase. Make the rectangle tall enough so that its upper boundary is beyond 2 milliamp (mA).

Click-and-draw rectangle around region of interest

• The Graph will rescale to fit the data in the area you selected.

➄ Click the “Smart Cursor” button ( ).

• The cursor changes to a cross-hair. The Y-coordinate of the cross-hair is displayed near the vertical axis. The X-coordinate of the cross-hair is displayed below the horizontal axis.

➅ Move the cursor/cross-hair to the point on the plot where the current reaches 2 milliamps.

Record the value of the turn-on

voltage (X-coordinate) at 2 mA in the Data Table.

Smart Cursor at 2 mA

X-coordinate, turn-on voltage

AC/DC Electronics Laboratory 012-05892A

PROCEDURE: Unit Two – Light-Emitting Diodes

PART I: Computer Setup

• You do not need to change the computer setup.

PART II: Sensor Calibration and Equipment Setup

➀ Prepare the red, yellow, and green LED’s by very carefully bending the wire leads so they can fit

in the component springs in place of the diode you used in Unit One.

➁ Replace the diode from Unit One with the first LED (red). Arrange the first LED so the short lead

(cathode) is to the left.

• The wire lead that is connected to the cathode of the LED is slightly shorter, and has a beveled shoulder near where the wire enters the LED.

PART IIIA: Data Recording – Light-Emitting Diodes

➀ Turn on the power switch on the back of the power amplifier.

Cathode - shorter,

beveled “shoulder” at the

top of the lead

➁ Click the “ON” button ( ) in the Signal Generator window.

➂ Click the “REC” button ( ) to begin data recording.

• Data recording will end automatically after 250 samples are measured. Run #2 will appear in the Data list in the Experiment Setup window.

➃ Click the “OFF” button ( ) in the Signal Generator window. ➄ Replace the first LED (red) with the next LED (yellow).

➅ Click the “ON” button in the Signal Generator window. Repeat the data recording procedure.

Click the “OFF” button in the Signal Generator window.

➆ Replace the second LED (yellow) with the last LED (green). Click the “ON” button in the Signal

Generator. Repeat the data recording. Click the “OFF” button in the Signal Generator.

• There should be four runs in the Data list in the Experiment Setup window.

Light-emitting diode (LED)

ANALYZING THE DATA: Light-Emitting Diodes

➀ Select “Save As…” from the File menu to save your data.

• The Graph display shows the three most recent runs of data (one run for each LED).

➁ Select “Run #2” from the bottom of the Experiment menu.

• The Graph display will show only Run #2.

➂ Click the “Autoscale” button ( ) to resize the Graph to fit the data.

012-05892A AC/DC Electronics Laboratory

➃ Click the “Magnifier” button ( ). The cursor changes to a magnifying glass shape. ➄ Use the cursor to click-and-draw a rectangle around the region of the plot of current and voltage

where the current begins to increase. Make the rectangle tall enough so that its upper boundary is beyond 2 milliamp (mA).

➅ Click the “Smart Cursor” button ( ). ➆ Move the cursor/cross-hair to the point on the plot where the current reaches 2 milliamps.

Record the value of the turn-on

voltage (X-coordinate) at 2 mA in Data Table 1.

➇ Select “Run #3” from the bottom of the Experiment menu. Repeat the analysis process for the

plot of Current versus Voltage for the second LED.

➈ Select “Run #4” from the bottom of the Experiment menu. Repeat the analysis process for the

plot of Current versus Voltage for the last LED.

DATA TABLE 1: Light-Emitting Diodes

Description Voltage (V) at 2 mA

1. Diode & 1 kΩ resistor

2. Red LED

3. Yellow LED

4. Green LED

PART IIIB: Data Recording - Bi-Color Diode

➀ Carefully bend the wire leads of the CLEAR (bicolor) light-emitting diode so they can fit in the

component springs in place of the last diode you used in Part IIIA of this Unit.

➁ Replace the green LED with the bicolor LED. ➂ Click the “ON” button ( ) in the Signal Generator window.

➃ Click the “REC” button ( ) to begin data recording.

• Data recording will end automatically after 250 samples are measured. Run #5 will appear in the Data list in the Experiment Setup window.

➄ Click the “OFF” button ( ) in the Signal Generator window. ➅ Describe the behavior of the bicolor LED during data recording. Put your observations in the

Data Table

➆ Turn off the power switch on the back of the power amplifier.

AC/DC Electronics Laboratory 012-05892A

ANALYZING THE DATA: Bi-Color LED

➀ Select “Save As…” from the File menu to save your data. ➁ Select “Run #5” from the bottom of the Experiment menu.

➂ Click the “Autoscale” button ( ) to resize the Graph to fit the data.

➃ Click the “Magnifier” button ( ). The cursor changes to a magnifying glass shape. ➄ Use the cursor to click-and-draw a rectangle around the region of the plot of current and voltage

where the current begins to increase on the RIGHT hand part of the plot. Make the rectangle tall enough so that its upper boundary is beyond 2 milliamp (mA).

➅ Click the “Smart Cursor” button ( ). ➆ Move the cursor/cross-hair to the point on the plot where the current reaches 2 milliamps. Record

the value of the turn-on

voltage (X-coordinate) at 2 mA in Data Table 2.

➇ Again click the “Magnifier” button ( ). ➈ Use the cursor to click-and-draw a rectangle around the region of the plot of current and voltage

where the current begins to increase on the LEFT hand part of the plot. Make the rectangle deep enough so that its lower boundary is below -2 mA.

➉ Click the “Smart Cursor” button ( ).

Move the cursor/cross-hair to the point on the plot where the current reaches -2 milliamps. Record

the value of the turn-on voltage (X-coordinate) at -2 mA in the Data Table 2.

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Data Table 2: Bi-Color LED

Description Voltage (V) at 2 mA Voltage (V) at -2 mA

5. Bi-Color LED

Questions

➀ In Unit One, what does the plot of Diode Current versus Voltage mean? ➁ In Unit Two, which LED has the lowest turn-on voltage? Which LED has the highest turn-on

voltage?

➂ In Unit Two, how does the forward turn-on voltage for the Bi-Color LED compare to any of the

colored LED’s? How does the reverse turn-on voltage for the Bi-Color LED compare to any of the colored LED’s?

➃ Contrast and compare the Bi-Color LED with a “Zener” diode.

AC/DC Electronics Laboratory 012-05892A

012-05892A AC/DC Electronics Laboratory

Experiment 16: Diode Lab – Part 2

EQUIPMENT NEEDED:

Purpose

In this experiment, diodes are used to rectify an AC signal, and to build part of the basic circuitry of a power supply.

Theory

A diode can be used to provide DC current from an AC source. In other words, the diode rectifies the AC current.

When the rectified current is smoothed by using electronic filters, the diodes make up part of a power supply.

Overview

There are several units to the Diode Lab. You completed the first two units in Part 1 (the previous experiment). You will complete Unit Three and Unit Four in Part 2 (this experiment).

Unit Activity

Three rectify a sine wave Four basic power supply

In the third unit you will rectify a sine wave generated by the Power Amplifier. In the last unit you will setup the basic circuitry for a power supply.

PROCEDURE: Unit Three – Rectifying a Sine Wave

PART I: Computer Setup

➀ Connect the Science Workshop interface to the computer, turn on the interface, and turn on the

computer.

➁ Connect one Voltage Sensor to Analog Channel A. Connect the second Voltage Sensor to

Analog Channel B.

AC/DC Electronics Laboratory 012-05892A

➂ Connect the Power Amplifier to Analog Channel C. Plug the power cord into the back of the

Power Amplifier and connect the power cord to an appropriate electrical receptacle.

➃ In the Physics Folder of the Science Workshop Experiment Library, open the document:

Macintosh: “P53 Diodes Part 2” / Windows: “P53_DIO2.SWS”

The document opens with a Scope display with a trace of voltage from Analog Channel A (V) and a trace of voltage from Analog Channel B (V), and the Signal Generator window which controls the Power Amplifier.

➤ NOTE: For quick reference, see the Experiment Notes window. To bring a display to the top,

012-05892A AC/DC Electronics Laboratory

➄ The Signal Generator is set to output 6.00 V, sine AC waveform, at 2.00 Hz.

➅ The periodic sampling rate is determined by the Scope display Sweep Speed. ➆ Arrange the Scope display and the Signal Generator window so you can see both of them.

PART II: Sensor Calibration and Equipment Setup

• You do not need to calibrate the Voltage Sensors or Power Amplifier.

➀ Connect the 1N-4007 diode (black with gray stripe at one end) between the component spring

next to the top banana jack and the component spring to the left of the banana jack. Arrange the diode so the gray stripe is at the left end.

➁ Connect the 1 kΩ resistor (brown, black, red) between the component spring next to the bottom

banana jack and the component spring to the left of the bottom banana jack.

➂ Connect a 5 inch wire lead between the component spring at the left end of the diode and the

component spring at the left end of the 1 kΩ resistor.

➃ Put alligator clips on the banana plugs of both

voltage sensors. Connect the alligator clips of the Channel A voltage sensor to the wires at both ends of the diode.

to Channel A

KIT NO.

➄ Connect the alligator clips of the Channel B voltage

sensor to the wires at both ends of the 1 kΩ resistor.

3.3Ω

➅ Connect banana plug patch cords from the output of

the Power Amplifier to the banana jacks on the AC/ DC Electronics Lab Board.

PART IIIA: Data Recording - Rectifying a

3 VOLTS MAX

Sine Wave with a Diode

➀ Turn on the power switch on the back of the power

amplifier.

Diode

➁ Click the “ON” button ( ) in the Signal

to Power Amp

Generator window.

➂ Click the “MON” button ( ) to begin data

monitoring.

Res

EM-8656

AC/DC ELECTRONICS LABORATORY

to Channel B

AC/DC Electronics Laboratory 012-05892A

• The “A” channel trace on the Scope display is the voltage across the diode. The “B” channel trace is the voltage across the resistor.

➃ To “capture” the data displayed in the Scope, click the “PAUSE” button ( ) to temporarily

halt data monitoring when both traces are completely across the Scope screen.

➄ To save the data for the top trace, click the top “Data Snapshot” button ( ) in the right hand

corner of the Scope display. This will open the “Data Cache Information” window.

➆ Enter information for the “Long Name”, “Short Name”, and Units, then click “OK”.

012-05892A AC/DC Electronics Laboratory

➇ Save the data for the other trace on the Scope display. Click the middle “Data Snapshot” button.

Enter the needed information in the “Data Cache Information” window and then click “OK”.

• The short names of the data caches will appear in the Data list in the Experiment Setup window.

➈ Click the “STOP” button. Click the “OFF” button ( ) in the Signal Generator window.

ANALYZING THE DATA: Rectifying a Sine Wave with a Diode

➀ Select “Save As…” from the File menu to save your data. ➁ Select “New Graph” from the Display menu.

➂ Change the input. Click the “Input Menu” button ( ). Select “Data Cache, Diode Volt-

age” from the Input Menu.

AC/DC Electronics Laboratory 012-05892A

➃ Click the “Add Plot” menu button ( ) at the lower left corner of the Graph. Select “Data

Cache, Resistor Voltage” from the “Add Plot” menu.

➄ Click anywhere on the vertical axis of the top plot (Diode Voltage). The “Enter Plot Y Scale”

window opens.

➅ Type in “6.5” for the Max and -6.5 for the Min, and then click “OK”. Repeat for the bottom plot

(Resistor Voltage)

• Both plots will have approximately the same scale for the vertical axis.

• Optional: If a printer is available, select “Print Active Display” from the File menu.

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PART IIIB: Data Recording - Rectifying a Sine Wave with a LED

➀ Remove the diode from the component springs. Carefully place a colored LED in the component

springs.

➁ Repeat the data recording procedure as in Part IIIA. ➂ After you finish recording data, turn off the power switch on the back of the power amplifier.

ANALYZING THE DATA: Rectifying a Sine Wave with a LED

➀ Repeat the data analysis procedure that followed Part IIIA.

• Optional: If a printer is available, select “Print Active Display” from the File menu.

PROCEDURE A: Unit Four – Power Supply, Single Diode

PART I: Computer Setup

➀ Remove the voltage sensor from Analog Channel A of the interface. ➁ Expand the Experiment Setup window to full size by clicking the “Zoom” box or the “Restore”

button.

➂ Click on the icon of the Voltage Sensor under Analog Channel A to highlight it.

Press the “delete” key on the keyboard. Click “OK” in the alert dialog window that opens.

➃ Delete the data caches from the Data list in the Experiment Setup window. Click on a data cache

and press the “delete” key on the keyboard. Click “OK” in the alert dialog window that opens.

➤ NOTE: To delete both data caches at once, hold down the Shift key and select both data caches.

AC/DC Electronics Laboratory 012-05892A

➄ Click on the Signal Generator window, or select it from the Experiment menu. Click on the

frequency to highlight it. Type in “60” as the new frequency, and press “enter” on the keyboard.

PART II: Sensor Calibration and Equipment Setup

• You do not need to calibrate the sensors.

➀ Replace the 1 kΩ resistor with a 100 Ω resistor in the component springs near the bottom banana

jack. The 100 Ω resistor will be the “load” resistor.

red

•

Diode

Power Amplifier

black

100 Ω

•

➁ Get the following items for use later in this experiment: 470 microfarad (µF) capacitor, 10 ohm

resistor, three 1N-4007 diodes.

PART IIIA: Data Recording – Single Diode Rectifier

➀ Turn on the power switch on the back of the power amplifier. ➁ Click the “ON” button ( ) in the Signal Generator window.

➂ Click the “MON” button ( ) to begin data monitoring.

• The “OUT” channel trace on the Scope display is the Output Voltage from the Power Amplifier. The “B” channel trace is the voltage across the resistor.

channel A

black

➤ NOTE: The trace of the Output Voltage has been offset downward so both traces can be seen.

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➃ Click the “STOP” button. ➄ Click the “Data Snapshot” button ( ) for the “B” channel. Enter Data Cache Information for

“Long Name”, “Short Name”, and Units as needed to save the data for analysis.

➅ Click the “OFF” button ( ) in the Signal Generator window.

PART IIIB: Data Recording – Diode and Capacitor

➀ Add the 470 µF capacitor in parallel to the 100 Ω resistor. Carefully bend the leads of the

capacitor so they can fit in the same component springs as the resistor. Put the shorter wire lead of the capacitor into the right hand component spring. The capacitor acts as a “filter”.

red

Power Amplifier

black

Diode

100 Ω

•

470 µF

•

10 Ω

••

red

channel A

black

➁ Click the “ON” button ( ) in the Signal Generator window.

➂ Click the “MON” button ( ) to begin data monitoring.

• The top trace is the voltage across the “load” resistor.

AC/DC Electronics Laboratory 012-05892A

➃ Click the “STOP” button. ➄ Click the “Data Snapshot” button ( ) for the “B” channel. Enter Data Cache Information for

“Long Name”, “Short Name”, and Units as needed to save the data for analysis.

➅ Click the “OFF” button ( ) in the Signal Generator window. ➆ Put the 10 Ω resistor in parallel with the 100 Ω resistor and the 470 µF capacitor. The 10 Ω

resistor simulates a motor or small light bulb.

➇ Click the “ON” button ( ) in the Signal Generator window.

➈ Click the “MON” button ( ) to begin data monitoring.

➉ Click the “STOP” button.

Click the “Data Snapshot” button ( ) for the “B” channel. Enter Data Cache Information for

“Long Name”, “Short Name”, and Units as needed to save the data for analysis.

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Click the “OFF” button ( ) in the Signal Generator window. Turn off the power switch on

the back of the power amplifier.

ANALYZING THE DATA: Power Supply, Single Diode

➀ Select “Save As…” from the File menu to save your data. ➁ Select “New Graph” from the Display menu.

➂ Change the input. Click the “Input Menu” button ( ). Select “Data Cache, Rectified

Voltage” from the Input Menu.

➃ Click the “Add Plot” menu button ( ) at the lower left corner of the Graph. Select “Data

Cache,

Filtered Voltage” from the “Add Plot” menu.

➄ Click again on the “Add Plot” menu button ( ) at the lower left corner of the Graph.

Select “Data Cache,

Load Resistor Voltage” from the “Add Plot” menu.

➅ Click anywhere on the vertical axis of the top plot (Rectified Voltage). The “Enter Plot Y Scale”

window opens.

AC/DC Electronics Laboratory 012-05892A

➆ Type in “6.5” for the Max and -6.5 for the Min, and then click “OK”. ➇ Click anywhere on the vertical axis of the middle plot (Filtered Voltage). Type in “10” and “-10”

for the Max and Min and then click “OK. Repeat for the bottom plot (

Load Resistor Voltage)

• Optional: If a printer is available, select “Print Active Display” from the File menu.

PROCEDURE: Unit Four – Power Supply

PART I: Computer Setup

• You do not need to change the computer setup.

PART II: Sensor Calibration and Equipment Setup

➀ Remove the 100 Ω resistor from the AC/DC Electronics Lab Board. ➁ Put the diode between the second and third component springs to the left of the top banana jack.

Place the diode so the gray stripe (cathode) end is to the right (toward the banana jack).

➂ Place a second diode parallel to the first between the second and third component springs to the

left of the bottom banana jack. Place the diode so the gray stripe (cathode) end is to the right (toward the banana jack).

➃ Place a third diode between the component spring at the right end of the top diode, and the

component spring at the right end of the bottom diode. Place the diode so the gray stripe (cathode) is toward the bottom.

➄ Place a fourth diode between the component spring at the left end of the top diode, and the

component spring at the left end of the bottom diode. Place the diode so the gray stripe (cathode) is toward the bottom.

• The diode arrangement forms a square.

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➅ Put the 100 Ω resistor

diagonally between the upper left corner and the lower right corner of the square of diodes.

Res

(4) Diode

to Power Amp

➆ Use a five inch wire lead to

connect a component spring next to the top banana jack

EM-8656

and the component spring at

AC/DC ELECTRONICS LABORATORY

the RIGHT end of the first diode.

to Channel B

➇ Use a ten inch wire lead to

connect a component spring next to the bottom banana jack and the component spring at the LEFT end of the second (bottom) diode.

red

Power Amplifier

black

100 Ω

black

channel A

➄ Connect the alligator clip of the red voltage sensor lead to the component spring at the upper left

corner of the diode square (called a “bridge”). Connect the alligator clip of the black voltage sensor lead to the component spring at the lower right corner of the diode bridge.

PART III: Data Recording - Four Diode Bridge Rectifier

➀ Turn on the power switch on the back of the power amplifier. ➁ Click the “ON” button ( ) in the Signal Generator window.

➂ Click the “MON” button ( ) to begin data monitoring.

AC/DC Electronics Laboratory 012-05892A

• The top trace is the voltage across the “load” resistor. (The other trace is the Output Voltage.)

➃ Click the “STOP” button. ➄ Click the “Data Snapshot” button ( ) for the “B” channel. Enter Data Cache Information for

“Long Name”, “Short Name”, and Units as needed to save the data for analysis.

➅ Click the “OFF” button ( ) in the Signal Generator window. ➆ Put the 470 µF capacitor in parallel with the 100 Ω resistor.

➇ Click the “ON” button ( ) in the Signal Generator window.

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➈ Click the “MON” button ( ) to begin data monitoring.

➉ Click the “STOP” button.

Click the “Data Snapshot” button ( ) for the “B” channel. Enter Data Cache Information for

“Long Name”, “Short Name”, and Units as needed to save the data for analysis.

Click the “OFF” button ( ) in the Signal Generator window.

Put the 10 Ω resistor in parallel with the 470 µF capacitor and the 100 Ω resistor.

Click the “ON” button ( ) in the Signal Generator window.

Click the “MON” button ( ) to begin data monitoring.

AC/DC Electronics Laboratory 012-05892A

Click the “STOP” button.

Click the “Data Snapshot” button ( ) for the “B” channel. Enter Data Cache Information for

“Long Name”, “Short Name”, and Units as needed to save the data for analysis.

Click the “OFF” button ( ) in the Signal Generator window. Turn off the power switch on the

back of the power amplifier.

ANALYZING THE DATA: Four Diode Bridge

➀ Select “Save As…” from the File menu to save your data. ➁ Select “New Graph” from the Display menu.

➂ Change the input. Click the “Input Menu” button ( ). Select “Data Cache, Full rectified

voltage” from the Input Menu.

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➃ Click the “Add Plot” menu button ( ) at the lower left corner of the Graph. Select “Data

Cache,

Filtered Full Rectified voltage” from the “Add Plot” menu.

➄ Click again on the “Add Plot” menu button ( ) at the lower left corner of the Graph.

Select “Data Cache,

Load Resistor Voltage” from the “Add Plot” menu.

➅ Click anywhere on the vertical axis of the top plot (Full rectified voltage). The “Enter Plot Y

Scale” window opens.

➆ Type in “10” for the Max and “-10 for the Min, and then click “OK”. ➇ Click anywhere on the vertical axis of the middle plot (Filtered Full Rectified Voltage). Type in

“10” and “-10” for the Max and Min and then click “OK. Repeat for the bottom plot ( Resistor Voltage)

Load

• Optional: If a printer is available, select “Print Active Display” from the File menu.

AC/DC Electronics Laboratory 012-05892A

Questions

➀ In Unit Three, how do the plots of voltage across the diode and voltage across the resistor com-

pare to a complete sine wave?

➁ Based on your previous investigate of diodes, why do the plots of voltage across the diode and

voltage across the resistor from the first part of Unit Three have the shape and size they do?

➂ In Unit Three, how did the plots of voltage across the diode and voltage across the resistor change

when the diode was replaced with the LED? Explain.

➃ In the first part of Unit Four, what happens to the trace of voltage across the diode when the

470 µF capacitor is put in parallel with the 100 Ω resistor? Why is the capacitor considered to be a “filter”?

➄ In the first part of Unit Four, what happens to the trace of voltage across the diode when the 10 Ω

resistor is added in parallel to the 470 µF capacitor and 100 Ω resistor?

➅ In the second part of Unit Four, how does the trace of voltage across the 100 Ω resistor in the four

diode bridge compare to the trace of voltage across the single diode in the second part of Unit Three?

➆ What happens to the trace of voltage across the four diode bridge when the 470 µF capacitor is

put in parallel with the 100 Ω resistor? How does the shape of this trace compare to the similar “filtered” trace in the third part of Unit Three?

➇ What happens to the trace of voltage across the four diode bridge when the 10 Ω resistor is added

in parallel? How does the shape of this trace compared to the similar “load resistor voltage” trace in the third part of Unit Three?

➈ Compare the performance of the single diode circuit to the four diode bridge as far as providing a

steady, constant direct current when a low resistance load is connected.

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Experiment 17: Transistor Lab 1 – The NPN

Transistor as a Digital Switch

EQUIPMENT NEEDED:

– Computer and Science Workshop™ Interface – Power Amplifier (CI-6552A) – Voltage Sensor (CI-6503) – AC/DC Electronics Lab Board (EM-8656) – Regulated DC power supply of at least +5 Volts – Banana plug patch cords (such as SE-9750)

Purpose

The purpose of this experiment is to investigate how the npn transistor operates as a digital switch.

Theory

The transistor is the essential ingredient of every electronic circuit, from the simplest amplifier or oscillator to the most elaborate digital computer. Integrated circuits (IC’s), which have largely replaced circuits constructed from individual transistors, are actually arrays of transistors and other components built from a single wafer-thin piece or “chip” of semiconductor material.

The transistor is a semiconductor device that includes two p-n junctions in a sandwich configuration which may be either p-n-p or, as in this activity, n-p-n. The three regions are usually called the emitter, base, and collector.

n-p-n

base

transistor

supply

collectorbaseemitter

Base

load

npn transistor symbol

Collector

Emitter

Base

Collector

Transistor package

In a transistor circuit, the current through the collector “loop” is controlled by the current to the base. The collector voltage can be considerably larger than the base voltage. Therefore, the power

dissipated by the resistor may be much larger than the power supplied to the base by its voltage source. The device functions as a

power amplifier (as compared to a step-up transformer, for example, which is a voltage amplifier but not a power amplifier). The output signal can have more power in it than the input signal. The extra power comes from an external source (the power supply). A transistor circuit can amplify current or voltage. The circuit can be a constant current source or a constant voltage source.

AC/DC Electronics Laboratory 012-05892A

A transistor circuit can serve as a ‘digitial’ electric switch. In a mechanical electric switch, a small amount of power is required to ‘switch on’ an electrical device (e.g., a motor) that can deliver a large amount of power. In a ‘digital’ transistor circuit, a small amount of power supplied to the base is used to “switch on” a much larger amount of power from the collector.

Here is some general information. A transistor is a three-terminal device. Voltage at a transistor terminal relative to ground is indicated by a single subscript. For example, V

is the collector

voltage. Voltage between two terminals is indicated by a double subscript: VBE is the base-toemitter voltage drop, for instance. If the same letter is repeated, it means a power-supply voltage: VCC is the positive power-supply voltage associated with the collector.

A typical npn transistor follows these “rules”:

➀ The collector must be more positive than the emitter. ➁ The base-to-emitter and base-to-collector circuits behave like diodes. The base-emitter diode is

normally conducting if the base is more positive than the emitter by 0.6 to 0.8 Volts (the typical forward “turn on” voltage for a diode). The base-collector diode is reverse-biased. (See previous experiments for information about diodes.)

➂ The transistor has maximum values of I

tion (I

) and temperature.

CVCE

, IB, and VCE and other limits such as power dissipa-

➃ If rules 1 – 3 are obeyed, the current gain (or amplification) is the ratio of the collector current,

, to the base current, IB. A small current flowing into the base controls a much larger current

flowing into the collector. The ratio, called “beta”, is typically around 100.

PROCEDURE

PART I: Computer Setup

➀ Connect the Science Workshop interface to the computer, turn on the interface, and turn on the

computer.

➁ Connect the Voltage Sensor to Analog Channel A. ➂ Connect the Power Amplifier to Analog Channel B. Plug the power cord into the back of the

Power Amplifier and connect the power cord to an appropriate electrical receptacle.

➃ In the Physics Folder of the Science Workshop Experiment Library, open the document:

Macintosh: “P54 Transistor Lab 1” / Windows: “P54_TRN1.SWS”

012-05892A AC/DC Electronics Laboratory

The document opens with a Graph display with a plot of “Vbase” (voltage to the base) in Volts (V) versus Time (sec), and a plot of “Vcollector” (voltage to the collector) in Volts (V) versus Time (sec), and the Signal Generator window which controls the Power Amplifier.

➤ NOTE: For quick reference, see the Experiment Notes window. To bring a display to the top,

➄ The “Sampling Options…” are: Periodic Samples = 200 Hz, Start condition is Analog Output =

0.01 V, and Stop condition is Samples = 200.

➅The Signal Generator is set to output ±1.60 V, sine AC waveform, at 1 Hz.

➆ Arrange the Graph display and the Signal Generator window so you can see both of them.

• The plot of “Vbase” versus Time shows the output from the Power Amplifier (Analog Output).

The plot of “Vcollector” shows the voltage drop across the 330 Ω resistor (Analog Channel A).

AC/DC Electronics Laboratory 012-05892A

PART II: Sensor Calibration and Equipment Setup

• You do not need to calibrate the Voltage Sensor or Power Amplifier.

➀ Insert the 2N3904 transistor into the socket on the AC/DC Electronics Lab Board. The transistor

has a half-cylinder shape with one flat side. The socket has three holes labeled “E” (emitter), “B” (base) and “C” (collector). When held so the flat side of the transistor faces you and the wire leads point down, the left lead is the emitter, the middle lead is the base, and the right lead is the collector.

Socket

E = Emitter

B = Base

Top view of transistor socket

2N3904 transistor

C = Collector

➤ CAUTION: Connecting the transistor incorrectly can destroy the transistor.

➁ Connect the 22 kΩ resistor (red, red, orange) vertically between the component springs at the left

edge of the component area.

➂ Connect the 330 Ω resistor (orange, orange, brown) horizontally between the component springs

to the left of top banana jack.

➃ Carefully bend the wire leads of the red light-emitting diode (LED) so it can be mounted between

component springs. Connect the LED between the component springs to the left of the 330 Ω resistor. Arrange the LED so its cathode (short lead) is to the left (away from the resistor).

➄ Connect a wire lead from the component spring at the base terminal of the transistor to the

component spring at the top of the 22 kΩ resistor.

➅ Connect another wire lead from the component spring at the collector terminal of the transistor to

the component spring at the left end of the LED.

➆ Connect a red banana plug patch cord from the top banana jack to the positive (+) terminal of the

DC power supply.

➇ Connect a black banana plug patch cord from the negative (-) terminal of the DC power supply to

the component spring of the emitter terminal of the transistor.

+5 v

red

Channel A

black

red

Power Amplifier

black

330 Ω

LED

2N3904

22 kΩ

npn

Transistor as Digital Switch

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➈ Connect a black banana plug patch cord from the negative (-) terminal of the Power Amplifier to

the negative terminal of the DC power supply.

➉ Put alligator clips on the banana plugs of the Voltage Sensor. Connect the red lead of the sensor

to the component spring at the right end of the 330 Ω resistor and the black lead to the left end of the resistor.

Connect the red lead (+) from the Power Amplifier with an alligator clip to the bottom of the

22 kΩ resistor.

to Channel A

Ground

–

22 kΩ Res

Transistor 2N3904

EM-8656

3 VOLTS MAX

LED

Cathode

330 Ω

Res

AC/DC ELECTRONICS LABORATORY

Power Supply

+5V

Power Amp

PART III: Data Recording

➀ Turn on the DC power supply and adjust its voltage output to exactly +5 Volts. ➁ Turn on the power switch on the back of the power amplifier.

➂ Click the “ON” button ( ) in the Signal Generator window.

• Observe the behavior of the LED. Write a description of what you observe.

➃ Click the “REC” button ( ) to begin recording data. Recording will stop automatically after

200 samples are measured.

• Run #1 will appear in the Data list in the Experiment Setup window.

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➄ Click the “OFF” button ( ) in the Signal Generator window. ➅ Turn off the power switch on the back of the power amplifier. Turn off the DC power supply.

ANALYZING THE DATA

➀ Click on the Graph to make it active. Select “Save As…” from the File menu to save your data. ➁ Click the “Autoscale” button ( ) to rescale the Graph to fit the data.

• Optional: If a printer is available, select “Print Active Display” from the File menu.

➂ Click the “Smart Cursor” button. The cursor changes to a cross-hair when you move it into the

display area.

• The X-coordinate of the cursor/cross-hair is displayed under the horizontal axis. The Y-coordinate of the cursor/cross-hair is displayed next to the vertical axis.

➃ Put the cursor at the point on the plot of Vcollector where the voltage first begins to increase

above zero. Hold down the Shift key.

Smart Cursor

➄ While holding the Shift key, move the cursor/cross-hair vertically along the dashed line until you

reach the point on the plot of Vbase that corresponds to the same point on the plot of Vcollector.

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Y-coordinate

Smart Cursor

➅ Record the Y-coordinate of that point on the plot of Vbase.

voltage _________ (V)

QUESTIONS

➀ What is the behavior of the LED when the circuit is active? ➁ How does the general shape of the plot for the Vbase compare to the plot of Vcollector for the

transistor?

➂ What is the voltage on the Vbase plot when the LED turns on (that is, when the Vcollector

voltage begins to rise above zero)?

➃ What is the relationship between the behavior of the LED and the point on the plot of Vcollector

when the voltage begins to rise above zero?

AC/DC Electronics Laboratory 012-05892A

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Experiment 18: Transistor Lab 2 – Current Gain:

The NPN Emitter-Follower Amplifier

EQUIPMENT NEEDED:

– Computer and Science Workshop™ Interface – Power Amplifier (CI-6552A) – (2) Voltage Sensor (CI-6503) – AC/DC Electronics Lab Board (EM-8656) – Regulated DC power supply of at least +5 Volts – Banana plug patch cords (such as SE-9750)

Purpose

The purpose of this experiment is to investigate the direct current (DC) transfer characteristics of the npn transistor, and to determine the current gain of the transistor.

Theory

Transistors are the basic elements in modern electronic amplifiers of all types. In a transistor circuit, the current through the collector “loop” is controlled by the current to the base.

n-p-n

transistor

collectorbaseemitter

supply

load

base

The voltage applied to the base is called the base bias voltage. If it is positive, electrons in the emitter are attracted onto the base. Since the base is very thin (approximately 1 micron), most of the electrons in the emitter flow across into the collector, which is maintained at a positive voltage. A relatively large current, IC, flows between collector and emitter and a much smaller current, IB, flows through the base.

A small change in the base voltage due to an input signal causes a large change in the collector current and therefore a large voltage drop across the output resistor, R

. The power dissipated

load

by the resistor may be much larger than the power supplied to the base by its voltage source. The device functions as a power amplifier. What is important for amplification (or gain) is the change in collector current for a given change in base current. Gain can be defined as the ratio of output current to input current.

A transistor circuit can amplify current or voltage.

AC/DC Electronics Laboratory 012-05892A

PROCEDURE

PART I: Computer Setup

➀ Connect the Science Workshop interface to the computer, turn on the interface, and turn on the

computer.

➁ Connect one Voltage Sensor to Analog Channel A. Connect the other Voltage Sensor to Analog

Channel B.

➂ Connect the Power Amplifier to Analog Channel C. Plug the power cord into the back of the

Power Amplifier and connect the power cord to an appropriate electrical receptacle.

➃ In the Physics Folder of the Science Workshop Experiment Library, open the document:

Macintosh: “P55 Transistor Lab 2” / Windows: “P55_TRN2.SWS”

The document opens with a Graph display of Output Current (mA) for Analog Channel B versus Input Current (mA) for Analog Channel A, and the Signal Generator window which controls the Power Amplifier (Analog Output).

012-05892A AC/DC Electronics Laboratory

➤ NOTE: For quick reference, see the Experiment Notes window. To bring a display to the top,

➄ The “Sampling Options…” are: Periodic Samples = 200 Hz, Start Condition is Analog Output =

0.01 V and Stop condition = Samples at 200.

➅ The Signal Generator is set to Amplitude 3.98 V, sine AC waveform, and Frequency 1.00 Hz.

➆ Arrange the Graph display and the Signal Generator window so you can see both of them.

• The Output Current (vertical axis) is calculated by dividing the voltage drop across the 1 kΩ

resistor (Analog Channel B) by the resistance. The Input Current (horizontal axis) is calculated by dividing the voltage drop across the 22 kΩ resistor (Analog Channel A) by the resistance.

PART II: Sensor Calibration and Equipment Setup

• You do not need to calibrate the Voltage Sensor or Power Amplifier.

➀ Insert the 2N3904 transistor into the socket on the AC/DC Electronics Lab Board. The transistor

Socket

E = Emitter

B = Base

Top view of transistor socket

2N3904 transistor

C = Collector

➤ CAUTION: Connecting the transistor incorrectly can destroy the transistor.

➁ Connect the 1 kΩ resistor (brown, black, red) vertically between the component spring at the left

edge of the component area on the AC/DC Electronics Lab Board.

➂ Connect the 22 kΩ resistor (red, red, orange) vertically between the component springs to the

right of 1 kΩ resistor.

➃ Connect a wire lead between the component spring next to the emitter terminal of the transistor,

and the component spring at the top end of the 1 kΩ resistor.

➄ Connect another wire lead betweeen the component spring next to the base terminal of the

transistor, and the component spring at the top end of the 22 kΩ resistor.

➅ Connect another wire lead betweeen the component spring next to the collector terminal of the

transistor, and the component spring next to the top banana jack.

AC/DC Electronics Laboratory 012-05892A

➆ Connect a red banana plug patch cord from the positive (+) terminal of the DC power supply to

the top banana jack.

➇ Connect a red banana plug patch cord from the positive (+) terminal of the Power Amplifier to the

component spring at the bottom end of the 22 kΩ resistor.

➈ Connect a black banana plug patch cord from the negative (-) terminal of the DC power supply to

the component spring at the bottom end of the 1 kΩ resistor.

➉ Connect a black banana plug patch cord from the negative (-) terminal of the Power Amplifier to

the negative terminal of the DC power supply.

Battery

to Channel B

Battery

–

1 kΩ Res

Ground

Transistor 2N3904

22 kΩ

Res

EM-8656

Power Amp

3 VOLTS MAX

AC/DC ELECTRONICS LABORATORY

to Channel A

Power Supply

+5V

red

Power Amplifier

black

Current gain:

+5 v

Channel

22 k

Ω

1 k

npn

Transistor Emitter-Follower Amplifier

2N3904

Ω

red

To Channel B

black

PASCO EM-8656 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual