Basic Electrostatics System
ES-9080B
30
®
3D.1: Capacitors in Series
Make sure all capacitors are uncharged before connecting them. (Use a short wire to
momentarily short each one.)
1.
Set up the series circuit, as shown in Figure 3.7a.
2.
Plug in to the 30 VDC output on the Voltage Source. Close switch A to charge capacitor
C1.
3.
Using the known value of
C
1
, calculate the initial amount of charge on
C
1
. Let’s call it
Q
o
.
(Remember
Q
=
CV
.)
4.
Throw the switch to position B.
C
1
and
C
2
are now in series.
5.
Use the electrometer to measure the voltage drop across each of the capacitors (
V
1
and
V
2
).
6.
Using the known values of capacitance, determine the amount of charge in each of them.
(
Q
1
and
Q
2
).
7.
Questions: Can you find a relation between
V
1
,
V
2
and the voltage of the source? How
does
Q
1
and
Q
2
relate to the original charge on
C
1
?
3D.2: Capacitors in Parallel
1.
Make sure all capacitors are uncharged before connecting them to the circuit.
2.
Set up the parallel circuit, as shown in Figure 3.7b.
3.
Set the voltage source to 30 VDC. Close the switch to charge the capacitors.
4.
Use the electrometer to measure the potential difference across each of the capacitors.
How does it compare to the voltage of the source?
5.
Use the known value of the capacitances to determine the charge in each capacitor. How
are the charges related?
Analysis:
1.
Compare series and parallel capacitors in terms of charges, voltages and capacitance.
