NEB Lecture Notes: Capacitor

Capacitors:

A capacitor is a device which store electric charges on it. Basically, it consists of 2 conducting surfaces separated by an insulating material or vacuum. The conducting surfaces are called plates and the insulating materials are called di – electric. There are various types of capacitors.

Capacitance of a capacitor:

The charge holding capacity of a capacitor is called its capacitance. When charge is given to the capacitor, the potential difference between the plates increase. If Q be the charge on either plate of the capacitor and V be the potential difference across the plates of the capacitor, then, it is given that,

[latex]Q \propto V[/latex].

Or, [latex]Q = CV[/latex], where, C is a constant called capacitance of a capacitor.

We have, [latex]C = Q/V[/latex]. Hence, the capacitance of a capacitor may be defined as the ratio of charge on either plate of the capacitor to the potential difference of the capacitor. The unit of capacitance is [latex]CV^{-1}[/latex] or Farad (F).

From the relation,

[latex]C = Q/V[/latex].

The capacitance of a capacitor is said to be 1 Farad if its potential difference rises by 1V when a charge of 1C is given to it. The smaller units of the capacitance are mF, μF (micro Farad), nF (nano Farad), where,

1 mF = [latex]10^{-3}[/latex] F

1 μF = [latex]10^{-6}[/latex] F

1 nF = [latex]10^{-9}[/latex] F