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

Options

A. the electric field E at all points on the x-axis has the same direction
B. work has to be done in bringing a test charge from `oo` to the origin
C. electric field at all point on y-axis is along x-axis
D. the dipole moment is along the x-axis

Answer

C, D

Explanation

The diagrammatic representation of the given question is shown in figure. The electrical field E at all points on the x-axis will not have the same direction. For `-d le x le d`, electric field is along positive x-axis while for all other points it is along negative x-axis. The electric field E at all points on the y-axis will be parallel to the x-axis `(i.e, hati)` The electrical potential at the origin due to both the charges is zero, hence no work is done in bringing a test charge from infinity to the origin. Dipole moment is direction from the +q charge to the charge `(i.e, -hati" direction")`.