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Capacitance And Capacitor
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Introduction

The capacitance of any conductor is its capacity to store charge. As the quantity of charge on conductor is increased its potential also increases. Beyond a limit even if a small additional charge is given then it starts leaking.

Hence Q µ V or Q = CV.

Where C is called capacitance of the conductor. It depends upon geometrical shape and size of the conductor.

If V = 1 volt, then Q = C, hence capacitance of any conductor will be numerically equivalent to that charge which makes its potential equal to 1 volt.

Unit of capacitance is ‘Farad’:

1 Farad = 1 coulomb/1 volt.

= coulomb/ (joule/coulomb).

= coulomb2/joule.

= (ampere x second) 2 / ( Newton x meter).

3) Dimensions of capacitance:

In practice 1 Farad is very large capacity therefore its small units are as following:

1)      1 micro-farad = 10-6 farad = 1mf.

2)      1 nano-farad = 10-9 farad = 1hf.

3)      1 pico-farad or micro-micro farad = 10-12 farad = 1rf = 1mmf.

4)

Capacitance of spherical conductor:

For a spherical conductor of radius R,

Potential is

Fig (1)

1)      .

2)      C µ R.

3)      C (capacitance) does not depend upon the charge given.

5) Energy stored in a charged conductor:

6) Redistribution of charge:

Fig (2)

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