Physics 220 (Section 1)
Lab #6 -- Capacitors

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Note: Items in red are measurements that must be made as you do the experiment.

Introduction

You will connect capacitors and batteries in various combinations and use a digital voltmeter to measure the potential differences (voltages) that arise due to charging. You should use the rules for parallel and series capacitance to predict the outcome of each configuration before making your measurement.

 

Getting Started:

Record the voltage of the battery and the capacitance of each capacitor.  Remove any leftover charge from each capacitor by simultaneously connecting both of its leads to the ground terminal


C1 =  F  (Use numbers such as 7, -3.54, 2.17E-12 for all entries.)

C2 = F

C3 = F

C4 = F

Vbattery =  V

Parallel:

Connect the battery to C1 to charge the capacitor; and then remove the battery.  Connect C1 to C3 in parallel as shown in Figure 1, while leaving the battery disconnected.  Disconnect all of the wires and separately measure voltages across C1 and C3. Record these values and compare them to your predictions.

Remember that capacitors connected in parallel have the same voltage, but the final voltage will be less than the voltage across the battery. (Why?) The other thing you need to remember is that charge is conserved.

Predicted Values:

VC1 =   V           VC3 =   V

Measured Values:

VC1 =   V           VC3 =   V

Figure 1

Series:

Connect all four capacitors in series with the battery as shown in Figure 2. Now disconnect all of the wires and separately measure the voltage across each capacitor. Record these values and compare them to your predictions.

Remember that capacitors connected in series have the same charge.

Predicted Values:

VC1 =   V           VC2 =   V

VC3 =   V           VC4 =   V

Measured Values:

VC1 =   V           VC2 =   V

VC3 =   V           VC4 =   V

 

Figure 2

Crossed:

As shown in Figure 3, connect C2 and C4 together in parallel with the battery.  Next, disconnect all of the wires.  Then cross-connect C2 and C4 so that the negative side of C1 is connected to the positive side of C4 and vice versa. Disconnect all wires and measure the voltage across each capacitor. Record and compare to predictions.

After the capacitors are cross-connected, they are in parallel, much as in the first case. This time, however, you must be careful with conservation of charge, as the positive plate of one capacitor is connected to the negative plate of the other capacitor!

Predicted Values:

VC2 =   V           VC4 =   V

Measured Values:

VC2 =   V           VC4 =   V

 

Figure 3