Question

$4$ charges are placed at follows:
$-2q$ at $(a,0)$
$q$ at $(0,-a)$
$-2q$ at $(-a,0)$
$3q$ at $(0,a)$
The dipole moment of the configuration is

• A. $2qa\hat{j}$
• B. $3qa\hat{j}$
• C. $2qa[\hat{i}+\hat{j}]$
• D. None of these

Answer 1

The correct option is A $2qa\hat{j}$


Net dipole moment $=\underset{i}{\Sigma }{q}_i{r}_i$

$=(a\times 3q)\hat{j}+(-2qa)\hat{i}+[-2(-a\left)\hat{i}\right]+q(-a)\hat{j}$

$⟹2qa\hat{j}$