Explain behaviour of dielectrics in an electric field.

1. In polar dielectric substances charge is not distributed symmetrically i.e. centres of positive and negative charges do not coincide even in the absence of electric field.
2. In non polar dielectric substances charge is distributed symmetrically i.e., centres of positive and negative charges coincide even in the absence of electric field.
3. When non-polar dielectric substances are placed in an external field E₀ in each molecule the centre of positive charge will be displaced in the direction of the field the centre of negative charge in the opposite direction.
4. Each molecule is said to get polarised. Let the magnitude of external electric field be E₀.
5. As the molecules are polarized in an electric field then surface charge will develop on each molecule and these induced charges are in opposite direction to the applied field.
6. These induced charges will develop electric field E_i in opposite direction.
7. Resultant electric field in the dielectric E = E₀ – E_i
8. Due to charge polarization, intensity of electric field in a dielectric reduces.
9. The value of actual intensity $\mathrm{E}=\frac{{\mathrm{E}}_0}{\mathrm{K}}$
So capacity increases by K times.