Question

Two point charges `+q` and `-q` are held fixed at `(-d,o)` and `(d,0)` respectively of a x-y coordinate system. Then
A. `E` at all points on the Y-axis is alon `hati`
B. the electric field `vecE` at all points on the X-axis has the same direction
C. dipole moment is `2qd` directed along `hati`
D. work has tobe done in bringing a test charge from infinity to the origin

Answer 1

Correct Answer - A
From the figure, it is clear that `vecE` at all points on the y-axis is along `hati`. Here `vecE` of all points on x-axis cannot have the same direction.
Here electric potential at origin is zero so no work is done in bringing a test charge from infinity to origin.

Here dipole moment is in `-x`direction `(-q to +q)`.
Hence only option (a) is correct.