question_answer

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 E at all points on \[x\]  -axis has the same direction.

B)  work has to be done in bringing a test charge from infinity to origin

C)  electric field at all points on y-axis is along \[x\]-axis

D)  the dipole moment is 2qd along the \[x\]  -axis.

Correct Answer: C

Solution :

[a] \[\vec{E}\] at all points on x-axis will not have same direction

[b] \[{{V}_{0}}=0,\] hence no work is done in bringing a test charge from infinity to origin

[c] \[\vec{E}\] at all points on y-axis will be parallel to x-axis because \[|{{\vec{E}}_{q}}|=|{{\vec{E}}_{-q}}|\]

[d] Dipole moment is directed along \[(-\vec{i})\] direction