Four charges `+q, -1, +q` and `-q` are placed in order on the four consecutive corners of a square of side a. The work done in interchanging the positions of any two neighbouring charges of the opposite sign is

Four charges + q, –q, + q and –q are put together on four corners of a square as shown in figure. The work done by external agent in slowly assembling this configuration is

Four equal charges Q are placed at the four corners of a square of each side is 'a'. Work done in removing a charge -Q from its centre to infinity is

Four point charges q, q, q and – q are placed at the vertices of a square of side length a. The configuration is changed and the charge are positioned at the vertices of a rhombus of side length a with – q charge at the vertex where angle is 120^(@) . Find the work done by the external agent in changing the configuration.

Three charges, each equal to q, are placed at the three. corners of a square of side a . Find the electric field at. the fourth corner.