# Electric Displacement

Physics

## definition

### Electric Displacement

Electric displacement is given as:

where:
External electric field
Polarisation
Permittivity of free space

It is related to the free charge density by,

Note:
1. Electric Displacement is directly related to the free surface charge density in a medium instead of the electric field.
2. On change of medium of an electric field, electric field changes but electric displacement remains the same.

## definition

### Relationship between Electric Displacement and Electric field

Electric displacement is given by:

where
Permittivity of the medium