question_answer

Electric charges \[q,\,q,\,-2q\] are placed at the corners of an equilateral triangle \[ABC\] of side \[l\]. The magnitude of electric dipole moment of the system is    [MP PMT 1994]

A)                    \[ql\]

B)                                      \[2ql\]

C)                    \[\sqrt{3}ql\]                                 

D)                                      \[4ql\]

Correct Answer: C

Solution :

\[{{p}_{net}}=\sqrt{{{p}^{2}}+{{p}^{2}}+2pp\cos 60{}^\circ }=\sqrt{3}p=\sqrt{3}\,ql\] (Q p = ql)