Charging a capacitor

Warning

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

Perform the setup in Figure 1 and turn the switch to position 1. The resistance is equal to 3.8MΩ and a capacitor with a capacity of C=2μF

starts counting time with a stopwatch simultaneously with powering the circuits with a DC[1] voltage source E=8V.

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

55

\(U_c(V)\)

0

1.35

2.1

2.92

3.8

4.50

5.01

5.40

5.85

6.1

6.1

6.1

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 = 7.5s