A regular hexagon of side 10 cm. has a charge of `5muC` at each of its corners. Calculate the potential at the centre of hexagon.

Charges 1mu coul each are placed at the corners of a squares of side 9 cm. Calculate the potential at the centre of the square.

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.

Four point charges each of 10 nano coulomb are placed at the four corners of a square of side 2 m each. Find the neat potential at the centre of the square.