Discharging a capacitor

Warning

Before connecting the capacitor make sure it's discharged by short-circuiting it.

To discharge the capacitor, disconnect the voltage source by turning the switch to position 2, and start counting time with a stopwatch simultaneously with disconnecting the voltage source. the capacitor discharges over time through the resistance R,

Note

Read the voltage of the capacitor terminal each 5 seconds and record the values in the following table.

\(t(s)\)

00

05

10

15

20

25

30

35

40

45

50

\(U_c(V)\)

0

3.85

2.92

2.00

1.52

1.12

0.62

0.28

0.1

0.02

0.02

Required work

a- On graph paper, plot the voltage Uc= f(t)

b- Determine the time constant, τ = RC; the abscissa of the point of intersection of this tangent with the limit voltage of the load

c- From the time constant ensure the value of C.

Method

Plot the tangent to the origin point and determine the time constant

Simulation

In this graph we found τ is 7.5s which is close to the calculated one τ = RC = 7.2s