question_answer

A charge q is placed at (1, 2, 1) and another charge -q is placed at (0, 1, 0), such that they form an electric dipole. There exists a uniform electric field\[\vec{E}=\left( 2\hat{i}+3\hat{j} \right)\]. The torque experienced by the dipole is-

A) \[q(-3\hat{i}+2\hat{j}+\hat{k})\]

B)        \[q(\hat{i}+\hat{j}+\hat{k})\]

C) \[q(3\hat{i}+\hat{j}+\hat{k})\]     

D)        None of these

Correct Answer: A

Solution :

[a] \[{{\vec{r}}_{12}}={{\vec{r}}_{2}}-{{\vec{r}}_{1}}\] \[\vec{\tau }=\vec{P}\times \vec{E}\]