Question

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

• A. the electric field $\overrightarrow{E}$ at all points on the $x-$ axis has same direction
• B. $\overrightarrow{E}$ at all points on the $y-$ axis is along $\hat{i}$
• C. $\overrightarrow{E}$ at all points on the $y-$ axis is along $-\hat{i}$
• D. $\overrightarrow{E}$ at all points on the $y-$ axis is along $\hat{j}$

Answer 1

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

The below diagram shows the electric field configuration of the dipole formed.

From the diagram, we can see that,

$\left(1\right).$ Electric field $\overrightarrow{E}$ at $+x-$ axis on point right to $-q$ is directed towards left and on points left to $-q$ is directed toward right.
Similar is the case for electric field $\overrightarrow{E}$ at negative $x-$ axis.

$\left(2\right).$ $\overrightarrow{E}$ at all points on the $y-$ axis is along $\hat{i}$.

Hence, option (b) is the correct answer.