Electric Field and Electric Field Lines:
The electric field is defined as the electric force a unit charge will experience at a given point in space. By moving the unit charge around, we can create a map of the electric field at various points. To represent that map, we draw electric field lines following the rules:
Electric Dipole: Two charges with equal magnitude but opposite polarity are called "Electric Dipole".
The Electric Potential and the Equipotential Lines:Relation between the Electric Field and the Electric Potential:
For a conservative force such as the electrostatic force, a potential energy is defined so that
ΔU = - W,
where U is the potential energy in Jouls, and W is the work done by the force. If we consider the force applied on a unit charge particle,which is by definition the electric field, the work done by that force will be related to change in the potential energy of that unit charge, that is the electric potential. In one dimension and for two locations that are infinitely close to each other, x_{1} and x_{2}, the relation between the elelectric field and the electric potential can be written as:
E_{x} = - (V(x_{2}) - V(x_{1})) / (x_{2} - x_{1}). ( Eq.1 )
For a three-dimensional case, similar relations must be written for the y and z directions.