Practical 10 - Investigation of the charging and dischaging of a capacitor to determine the time constant

Question 1

Equation for the potential difference across a capacitor and the meaning of the symbols

Answer 1

V = Voe^-t/RC

V = p.d at time t
Vo = p.d at t=0
C = capacitance
R = circuit resistance
t = time

Question 2

Method

Answer 2

1. The circuit is set up and the capacitor is charged
2. The switch is moved to he discharge position and the timer is started
3. The value of the potential difference across the capacitor is notes at intervals of 20 seconds
4. This is done for a maximum time of about 300 seconds

Question 3

What do we need to make sure that we do in this experiment?

Answer 3

A pre-test

Question 4

Take logs of the equation used to show how it’s used to plot a graph

Answer 4

ln (v) = ln (Vo) - 1/RC x t

Gradient = 1/RC
RC = 1/gradient
1/gradient = x
RC = x
R = x/C

Question 5

Where do we find the value of C, the capacitance?

Answer 5

Written on the capacitor