Question

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 $\overrightarrow{E}$ at all points on the X-axis has the same direction
• B. $\overrightarrow{E}$ at all points on the Y-axis is along positive $\hat{i}$
• C. Work has to be done in bringing a test charge from infinity to the origin along the Y axis
• D. The dipole moment is 2qd directed along positive $\hat{i}$

Answer 1

The correct option is B $\overrightarrow{E}$ at all points on the Y-axis is along positive $\hat{i}$

The diagram representation of the given problem is shown in figure. The electrical field $\overrightarrow{E}$ at all points on the X-axis will not have the same direction.

The electric field $\overrightarrow{E}$at all points on the Y-axis will be parallel to the X-axis (i.e. $\hat{i}$ - direction).
The electric potential at the origin due to both the charge 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 +q charge (i.e. -x direction).