Q:Two point charges +q and -q are held fixed at (-d, 0) and (d, 0) respectively of a (x, y) coordinate system, then

(A)the electric field at all points on the x-axis has the same direction.

(B) E at all points on the Y-axis is along î.

(C)No Work has to be done in bringing a test charge from infinity to the origin.

(D)the dipole moment is 2qd directed along î.

Solution : E at all points on the y-axis is along . Electric potential at origin is zero so no work is done in bringing a test charge from infinity to origin.

Hence (C) is correct.