School of Physics Lecture Demonstration Manual

El-4 The Capacitor

Published: Tuesday 14 March 2006 - Updated: Thursday 31 March 2011


To demonstrate that the capacitance of a parallel plate capacitor is inversely proportional to d the distance of separation.



Click on pictures to enlarge.

The Capacitor

Capacitor Diagram


The Capacitor


The plates of the capacitor have been shellaced so that they can be brought into contact without shorting. In this position 9V is applied momentarily to the capacitor. No deflection is noted on the electroscope. On separating the plates the electroscope leaves diverge demonstrating that the voltage has increased and the capacitance decreased satisfying the relations

C=Q/V , C= A/d

It is worthwhile noting that for a modest deflection of the electroscope approximately 1000volts is required.

Safety notes

Electrical safety 


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