Four point charges q, -q, 2q and - 2q are placed at the comers of a square of side 5 cm. If `q= 5 * 10^-6 C`, find the magnitude of the electric field at the intersection of the diagonals.

Three charges, each equal to 16 * 10^-9 C are placed at the three corners of a square of side 4 cm. Find the electric field at fourth corner.

What are the magnitude and direction of the electric field at the centre of square in figure if q=1xx10^4 C and a = 5cm.

ABCD is a square of side 20 cm positive charges of +2 * 10^-9 C. +4 * 10^-9 C and + 8 * 10^-9 C are placed at the corners A, B and C respectively. Calculate the work required to be done to transfer a unit positive charge from D to the point of intersection of the diagonals.