Three point charges of `+2q,+2q and -4q` are placed at the corners A, B and C of an equilateral triangle ABC of side x. The magnitude of the electric dipole moment of this system is

Options

A. E along AO
B. 2E along AO
C. E along BO
D. E along CO

Answer

A

Explanation

Resolve E along CO and BO into two perpendicular components

The sine components cancel each other
The cosine components add up along OA to give `2E cos 60^@`
`:.` Resultant field along `AO = 2E - 2E cos 60^@`
`=2E - E = E`
`:.` Resultant field is E along AO .