This PPT gives an introduction to capacitors

1. CAPACITORS
Dr.R.Hepzi Pramila Devamani,
Assistant Professor of Physics,
V.V.Vanniaperumal College for Women,
Virudhunagar

2. Capacitance of a capacitor
 If a charge q is given to an isolated conductor its voltage is increased by an amount V.
 For a given conductor the ratio Q/V is independent of Q and depends on the size and shape of the
conductor.
 The ratio Q/V is called the capacitance of the conductor and is denoted by C. C = Q/V
 The capacitance of a conductor is defined as the amount of charge that should be given to it to
increase its potential by unity.

3. PRINCIPLE OF A CAPACITOR
 Suppose an insulated metallic plate A is
given a positive charge Q and its
potential is V. Its capacitance C = Q/V.
 Let another insulated metal plate B be
brought near A.
 Negative charge is induced on the side
of B which is nearer to A.

4. PRINCIPLE OF A CAPACITOR
 An equal positive charge is induced on the other side of B. The
negative charge on B decreases the potential of A.
 The positive charge on B increases the potential of A. But the
negative charge on B is nearer to A than the positive charge on B.
 So the net effect is that the potential of A decreases. Thus the
capacitance of A is increased.
 The positive charge on B is neutralized by connecting the
backside of B to earth. Then the potential of A decreases still
further. Thus the capacitance of A is increased.

5. PRINCIPLE OF A CAPACITOR
 A capacitor consists of two conductors one
positively charged and the other earthed. The
conductors are called plates.
 Capacitance depends on the geometry of the
conductors and th permittivity of the medium
separating them.
 A capacitor is a device for storing charge.

6. THANK YOU