3B Scientific Plate Capacitor D User Manual
3B SCIENTIFIC
Plate Capacitor D 1006798
Instruction sheet
06/12 SP/TL/ALF
1. Safety instructions
®
PHYSICS
1 Fine adjustment screw
2 Guide rail
3 Measuring unit
4 Switch for changing
measuring unit from
mm to inches
5 On-off switch for
measuring unit display
6 Zero configuration but-
ton for measuring unit
7 Battery compartment
for measuring unit
(button/watch battery)
8 Scale for measuring
unit
9 Fastening screw
10 Guide block
11 Connector socket
12 Movable capacitor pla-
te
13 Fixed capacitor plate
14 Stator
15 Connector socket
2. Description
Caution: the capacitor plates are not electrically
isolated. Voltages may be present which are
dangerous to the touch.
• When working with voltages which may be
dangerous if you come into contact with
them, you should make sure to take the appropriate safety measures.
• Do not touch the device during the experi-
ment.
• For voltages which are referenced to
ground, apply the reference potential to the
movable capacitor plate.
• Avoid voltage arcs between the plates.
In schools and educational institutions, operation of the device must be monitored by a
trained supervisor.
The plate capacitor is designed for investigating the
relationship between charge and voltage, for quantitative measurement of capacitance as a function of
the plate separation, measurement of dielectric ε
and for accurately determining the permittivity of
free space (electric field constant) ε
The apparatus features one fixed and one movable plate. The latter can be along with its guide
block (10) by any distance between 0 and
160 mm and can be further adjusted by between
0 and 20 mm by means of a fine adjustment
screw (1). The display of an electronic measuring
unit shows the distance between the two capacitor plates. The displayed value can be configured
to zero at any point along the path of travel and
will then display the distance of the moveable
plate from this new zero point. The separation
between the plates can be read off to an accu-
1
.
0
racy of 1/10 mm. A switch (5) can turn the display
⋅=τ
⋅
of the measuring unit on or off, while the actual
measurement acquisition continues. Another
switch (4) switches the units for the display between mm and inches.
3. Technical data
Plate surface area: 500 cm2
Plate thickness: 3 mm
Plate spacing: 0 – 160 mm
• Before using the measuring unit, configure
the display to zero with the two plates closed
together. Push the movable plate gently
against the fixed stator plate and then press
the zero configuration button (6).
The fine adjustment screw is to aid with precise
adjustment of the distance when the separation
between the plates is small. The guide block
(10) should also be gently pressed against the
adjustment screw.
Accuracy: 1/10 mm
Measuring unit: Electronic
0….160 mm
Battery for measuring unit: LR44
Dimensions: 400 x 260 x 340 mm³
Weight: 4 kg approx.
4. Operation
4.1 General notes
Never hold the plate capacitor apparatus other
than by the guide rail (2) and the stator (14).
Conducting deposits on insulating plastic parts
of the capacitor plates could lead to errors in
measurements.
• Before use, clean the apparatus with a dry,
microfibre cloth.
• Protect the guide rail (2) from dirt and dust.
If necessary, you should clean it using a thin
brush or cloth.
• After use, close the plates together and se-
cure them with the fastening screw (9) for
storage.
• Store the apparatus in a dry, dust –free loca-
tion.
If the plate capacitor apparatus has not been
used for a long period, it is possible to remove
the watch battery from the measuring unit.
• Do not dispose of the
Measurement of electric field constant ε0
The following equipment is also required to complete the experiment:
1 Function generator, FG 100 (230 V, 50/60 Hz)
1009957
or
1 Function generator, FG 100 (115 V, 50/60 Hz)
1009956
1 Precision resistor, 10 kΩ 1000685
1 Analogue oscilloscope 2x 30 MHz 1002777
1 HF patch cord, BNC/4 mm plug 1002748
Leads for experiments
• Set up the experiment as shown in Fig. 2.
• Charge up the plate capacitor via the resistor
at regular intervals using the function generator (square wave voltage). The frequency
should be between 10 and 50 kHz.
Due to the capacitance C of the plate capacitor,
the current (measured via the voltage across the
resistor U
exhibits a periodic exponential curve over time
and is characterised by the time constant τ.
)(
R
• From the voltage traces on the oscilloscope,
determine the time t
drop to half of the applied voltage.
battery in the regular
household garbage.
Follow the local
regulations (In Germany: BattG; EU:
2006/66/EG).
4.2 Preparation
• Perform the experiment on a level surface
Fig. 1 Voltage curve as traced using an oscilloscope
where the apparatus cannot tip over.
=
• Make sure the wires to the plates are as
short as possible.
C (3)
R
5. Sample experiment
) during charging and discharging
R
CR
(1)
τ−⋅=/
t
eUtU (2)
0
taken for the voltage to
0
t
0
2ln
2
Loading...