Explain the behaviour of dielectrics in an external field.

Explanation

1. When an external field is applied across dielectrics, the centre of positive charge distribution shifts in the direction of electric field and that of the negative charge distribution shifts.

opposite to the electric field and induce a net electric field within the medium opposite to the external field. In such situation the molecules are said to be polarised.
2. Now consider a capacitor with a dielectric between the plates. The net field in the dielectric becomes less.
3. If `E_0` is the external field strength and `E_1` is the electric field strength induced , then the net field `hat(E)_("net")=hat(E)_(0)+hat(E)_(1)`
`(E_"net")=E_(0)-E_(i)=(E)/(K)` where K is the dielectric constant of the medium.