Question

Two charges $2\mu C$ and – $2\mu C$ are placed at points $A$ and $B,6cm$ apart.
i) Identify an equipotential surface of the system
ii) What is the direction of the electric field at every point on this equipotential surface?

Answer 1

i) An equipotential surface is defined as the surface over which potential is same everywhere.


Since the charges of same magnitude and opposite nature are present, therefore net electric potential due to both will be zero and thus equipotential surface will have zero potential everywhere.


Also, since the magnitude of charges are same, therefore the point of zero potential will be at the mid point of line joining the two charges.
Therefore, equipotential surface will be at the mid point and perpendicular to the line joining the two charge.



ii) At every point on this surface the direction of the electric field is normal to the plane in the direction of $AB$.