Charging a capacitor at a constant rate

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TAS Experimental Worksheet

Experiment P: Charging a capacitor at a constant rate

Marks : ______________

Aim: To investigate how the charge on a capacitor is related to the p.d. applied across it by charging the capacitor at a constant rate.

Apparatus:

o Capacitor (electrolytic type) 500 ?F

o Microammeter 100 ?A

o Clip component holder

o Stop-watch

o CRO

o Connecting leads

Theory:

From definition, the capacitor C of a capacitor is found from

C = Q/V

Where Q is the charge stored on the capacitor and V is the potential difference across it.

==> Q = CV

==>

If a capacitor is charged up at a constant rate, i.e. , where I is a constant.

Then is also constant.
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Hence the potential difference across the capacitor increases linearly with time.

Procedure

. The circuit was connected as shown in the figure below. The CRO was set to d.c. and the sensitivity to 1 V/cm.

2. The time base was set to any high value so that a steady horizontal trace is displayed. The trace was shifted to the bottom of the screen.

3. The capacitor was shorted out by connecting a lead across it and adjust the 100 k ? potentiometer for a suitable current, say 80 ?A.

4. Shorting lead ...

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