Justin Geeslin

Eng Physics II - M 1:00

Experiment Six – Capacitors


  1. Introduction

This experiment on capacitors will introduce the capacitor as a secondary power source; one whose variance of charge is a function of time. The circuits composed in this experiment will show the interactions of capacitors and resistors in the absence of a constant power source

  1. Procedure

The first circuit will feature a resistor of 100-kΩ and a 10-μF capacitor. There is also a switch that will allow the power source of the circuit to change. The switch will allow and disallow the battery to the circuit. When the circuit is closed, this will allow the capacitor to be discharged about the circuit. Whereas, when the battery is connected the capacitor will be charging instead of discharging. First, allow the capacitor to charge for about 30s. Then, flip the switch which will allow the capacitor to discharge across the circuit and begin collecting your data. Once the capacitor is fully discharged, record the data of the graph. Since the capacitor is fully discharged, the re-charge of the capacitor should be recorded. When the switch is flipped allowing the battery to discharge across the circuit, the capacitor will become charged. Record the data as the capacitor is becoming charged. This process will be repeated across the second circuit which will feature a 47-kΩ resistor in place of a 100-kΩ resistor used in circuit one. Data should be as follows:

Trial

A

B

C

1/C

R(kΩ)

C (μF)

RC (s)

Discharge 1

27.69

0.01834

0.9

1.1

100

10

1

Charge 1

20.95

-16.6

0.9

1.1

100

10

1

Discharge 2

6.135

0.012

1.9

0.53

47

10

.47

Charge 2

8.672

-4.303

1.907

0.52

47

10

.47

  1. The time constant, RC, will be the product between the amount of resistance and the capacity of the capacitor. For example, in the first discharge, there is a resistance of 100,000 ohms and 1 x 10-5. Those two values multiplied together will return 1 which is the time constant.

  2. The inverse of the scalar C is always similar to the time constant.

  3. Yes, there is a level of tolerance on each component that may account for the discrepancy. Outside factors such as temperature are something to take into account.