CAPACITOR OR CONDENSER
Define a capacitor. Give symbol, types, purpose and uses of capacitor.
Capacitor: A capacitor consists of two conductors of any shape separated by a non-conducting medium (insulator or dielectric) such that it can store electric charge.
When the capacitor is charged by connecting the two uncharged conductors to the terminals of a battery, the two conductors carry charges of equal magnitude but of opposite sign.
Now, when the battery is disconnected, the charges on the conductors remain the same. Hence, the capacitor stores the charge.
The potential difference (V=V1−V2) between the two conductors is the potential difference across the capacitor. This potential difference (V) is proportional to the charge (q) on the capacitor. That is,
V∝q
q=CV ... (1)
where C is known as the capacitance of the capacitor.
Therefore,
C=qV ... (2)
Thus, capacitance (C) of a capacitor is defined as the ratio of the magnitude of the charge q on the capacitor to the magnitude of the potential difference (V=V1−V2) between the conductors of the capacitor.
The net charge on the capacitor is zero because both conductors of a capacitor have equal and opposite charge but the magnitude of charge on either conductor is referred to the charge on the capacitor.
Symbol:
Types: Capacitors are named on the basis of the shape of the conductors used i.e., parallel plate, spherical, cylindrical etc. or on the basis of the name of dielectric medium i.e., electrolytic, paper, mica, ceramic etc.
Purpose: It is used to store electric charge. While storing charge, it also stores electrical energy for a small period. It can safely absorb large amounts of charge. Similarly, large amount of charge can be released by it.
Uses: It is used in electrical appliances such as fans, motors, voltage correctors, power factor improvers etc. and in electronic instruments, appliances, radio sets, television sets, computers etc.