PASCO ET-8781 User Manual

Instruction Manual

Manual No. 012-08780A

Mechanical

Equivalent of Heat Tube

Model No. ET-8781

Equivalent of Heat Tube Model No. ET-8781

Table of Contents

Equipment List........................................................... 3

Introduction ............................................................. 4

Theory ................................................................... 4

Equipment Setup ........................................................ 5

Suggested Experiment .................................................. 6

Sample Data/Results.................................................... 7

Appendix A: Technical Support ........................................ 8

Appendix B: Copyright and Warranty Information ................... 8

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Model No. ET-8781 Mechanical Equivalent of Heat Tube

M e ch an i c a l Eq u i va le n t

of Heat Tube

Model No. ET-8781

Equipment List

1

4

Included Equipment Replacement

1. Mechanical Equivalent of Heat Tube(1)

2. Fast Response Thermistor Probe (1 built-in probe)

3. Metal Balls (120 balls)

4. Velcro® Strip

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3

Model Number*

ET-8781

PS-2517

699-043

616-153

*Use Replacement Model Numbers to expedite replacement orders.

Additional Equipment Required Replacement

Model Number

PASCO computer interface (PASPORT™ or

DataStudio® software (version 1.8.5 or later)

Temperature Sensor

A computer

ScienceWorkshop

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)

PS-2125* or PS-2143* or

Various

(See PASCO catalog.)

Various

(See PASCO catalog.)

PS-2146* or CI-6527A**

NA

*

PAS PO RT

**

ScienceWorkshop® sensors require a ScienceWorkshop interface.

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™

sensors requires a PASPORT interface.

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Mechanical Equivalent of Heat Tube Model No. ET-8781

Introduction

PASCO’s Mechanical Equivalent of Heat Tube (ET-8781) is used for demonstrating changes
in gravitational energy to thermal energy. While the energy conversion is occurring, students
can measure and observe the temperature change in real-time in a DataStudio display.

As the tube is turned over, the steel balls fall the length of the tube and strike the thin, metal
plate at one end. Fastened to the bottom of the metal plate is a fast-response thermistor for
continuously measuring the temperature of the plate. The thermistor can be directly plugged
into either a PASPORT Temperature Sensor or a ScienceWorkshop Thermistor Sensor.
Students can then use DataStudio to measure the temperature increase caused by the impact.
In addition, students can measure the mass of the falling balls and the distance over which
they fall to calculate the change in gravitational energy.

The Mechanical Equivalent of Heat Tube is typically used in conservation of energy studies.
The tube can also be used as an analogy for the “disappearance” of kinetic energy during a
collision.

Theory

mb= mass of the steel balls

mp= mass of the aluminum plate

cb=specific heat of the steel balls

cp=specific heat of the aluminum plate

∆

T=change in the temperature

L=length of the tube

Q=thermal energy (heat)

PE= gravitational potential energy

Potential Energy

The change in gravitational potential energy of the balls as they fall a distance h is given by
PE=mgh. If the tube is held vertically at its center and rotated 180 degrees, the balls fall a
distance of L, the length of the tube. If the tube is then rotated back to the initial position, the
balls again fall a distance of L. Note that it is important that your hand stay at a constant
height during rotation. Thus, the balls fall a total distance of h=2L for each back and forth
rotation, and the total change in gravitational potential energy of the balls is

PE=mbg(2L) (1).

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Model No. ET-8781 Mechanical Equivalent of Heat Tube

Thermal Energy

When the balls strike the aluminum plate, their kinetic energy is converted into thermal

energy, increasing the temperature of the plate and the balls. For a single object, Q=mc ,

∆T

but since the balls and the plate have different specific heats, we need to account for each.
Also, there are two identical plates. You cannot remove the bottom plate. It is assumed that

∆T

is the same for all of the objects.

Q=[m

+ mpcp]

bcb

∆T

(2)

Equipment Setup

1. Plug the stereo plug of the Mechanical Equivalent of Heat Tube into a PASPORT

Temperature Sensor or ScienceWorkshop Thermistor Sensor.

2. Plug the Temperature Sensor into a PASPORT computer interface. (Note: If you are using

a ScienceWorkshop interface, plug the Thermistor Sensor into an analog channel of a
ScienceWorkshop computer interface. From the Sensors list, drag the Thermistor icon to
the same channel in the Setup window.

3. Use the Velcro strap to hold the cord against the tube.

4. Click the Start button. Turn the tube upside down and back up again. Repeat several

times. Watch the temperature change in DataStudio. To stop data collection, click the

Stop button.

Note: Do not use the Mechanical Equivalent of Heat Tube in direct sunlight. Using the

tube in direct sunlight will skew your results.

Figure 1: Heat
Tube connected
to a Temperature
Sensor and a
PASPORT
interface

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Mechanical Equivalent of Heat Tube Model No. ET-8781

Suggested Experiment

Exploring Energy Changes During the Rotation of a Heating Tube

Equipment required: Mechanical Equivalent of Heat Tube (ET-8781), DataStudio software,
computer interface (PASPORT or ScienceWorkshop), Temperature Sensor

Note: The Heat Tube must be used with a Temperature Sensor that accepts a stereo plug input
(i.e. PS-2125 Temperature Sensor, PS-2143 Quad Temp. Sensor, PS-2146 Absolute Pressure/
Temp. Sensor, or CI-6527A Thermistor Sensor)

1. Connect the Heat Tube to a Temperature Sensor and computer interface (For instructions, see

steps 1 and 2 under “Equipment Setup.”)

2. Launch DataStudio. In DataStudio’s Experiment Setup window, set the sample rate to as

fast as possible. In the Data list, double click on the Temperature icon to open the Data
Properties dialog. In the Data Properties dialog, set the accuracy to 0.01 and the precision
to 2. Click the OK button.

3. Pull off the cap on the heating tube. Weigh the mass of enough steel balls to cover one

layer on the surface of the aluminum plate on the inside of the tube.

4. Remove the aluminum plate from the plastic cap. Weigh the plate.

5. Put the balls in the tube. Reinsert the aluminum plate and push the cap back tight on the

tube.

6. Measure and record the length of the tube.

7. In DataStudio, open a Graph display and click the Start button. Hold the Heat Tube

upright in a vertical position with the cord end at the bottom. Hold the tube in the center
with your hands over the Velcro strap. Keep your hand at the level on the tube. Turn the
tube upside down and back up. Watch the temperature change in DataStudio.

8. Rotate the tube back and forth three times. Record the biggest change in the temperature.
(Note: To record the change, use the Smart Tool. In the Graph display, click on the Smart
Tool button. Hover the pointer over the box until the pointer becomes two double-headed
arrows. Drag the arrows to the desired location. The x and y coordinates appear to the right
of the arrows.

9. Calculate the loss in gravitational potential energy for one back and forth motion. Use

equation 1 for the calculation.

10. Calculate the increase in thermal energy of the balls and plates for the largest

temperature change, , using equation 2.

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∆T

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Model No. ET-8781 Mechanical Equivalent of Heat Tube

11. Calculate the percentage of energy turned into heat using .

%=Q/PE x 100(%)

12. Where did most of the energy go?

13. Repeat steps 3-12 with twice the number of balls and one-half the number of balls.

14. How does the temperature and potential energy (PE=mgh) change when you change the

number of balls? Why? Explain your results.

Sample Data/Results

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Mechanical Equivalent of Heat Tube Model No. ET-8781

Appendix A: Technical Support

For assistance with the ET-8781 Mechanical Equivalent of Heat Tube
or any other PASCO products, contact PASCO as follows:

Address: PASCO scientific

10101 Foothills Blvd.

Roseville, CA 95747-7100

Phone: [phone]

FAX: [phone]

Web: www.pasco.com

Email: [e-mail]

Appendix B: Copyright and Warranty Information

Copyright Notice

The PASCO scientific 012-08780A Mechanical Equivalent of Heat Tube Manual is
copyrighted and all rights reserved. However, permission is granted to non-profit educational
institutions for reproduction of any part of the 012-08780A Mechanical Equivalent of Heat
Tube 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.

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