An electric charge Q is uniformly distributed around a semi-circle of radius a. Calculate the electric potential at the centre of this semi-circle.

An electric charge Q is uniformly distributed around a thin metallic circular coil of single turn and of radius a. Find the expression for the electric potential at a point on its axis at a distance X form its its centre.

A hollow spherical conductor of radius 2m carries a charge of 1nC . The electric potential at the centre of the spherical conductor is