QS Study

Demonstrative experiment on Capacitance

Capacitance increases if areas of the two plates are increased; again it decreases if areas are decreased. Demonstrate the experiment.

Capacitance is the ability to store electrical energy. Almost all things, including you, can store some electrical energy and therefore have capacitance. When you rub your feet across a carpet, charged particles called electrons can be transferred from the carpet to you.

Two plane metallic plates A and B are fixed vertically on a platform [Figure]. Anyone of the plates (say A) is connected by a wire with an uncharged electroscope and the other plate (in this case B) is connected to the ground. Now by keeping two plates parallel and very close to each other, if the plate A is charged the leaves of the electroscope will diverge. Amount of divergence indicates the potential of A. Now keeping the separation between the plate unchanged, the plate is slowly pulled sideways as a result of which their general area decreases. It will be seen that the divergence of the leaves increases i.e., the potential difference between the plates is increasing. So if the general ‘a’ is decreased, then the capacitance of the capacitor decreases. Its reverse step is also true.