Relation between electric field and potential
Let the small distance between A and B be dx. Work done in moving a unit positive charge from A to B is dV=E.dx.
The work has to be done against the force of repulsion in moving unit positive charge towards the charge +q. Hence,
The change of potential with distance is known as potential dradient, hence the electric field is equal to the negative gradient of potential.
The negative sign indicates that he potential decreaces in the direction of electric field.The unit of electric intensity an also be expressed as Vm-1