Two north poles each of pole strength `m` and a south pole of pole strength `m` are placed at the three corners of an equilateral triangle of side a. The intensity of magnetic induction field strength at the centre of the triangle is

Options

A. `mu_(0)/(4pi)m/a^(2)`
B. `mu_(0)/(4pi)(6m)/a^(2)`
C. `mu_(0)/(4pi)(9m)/a^(2)`
D. `mu_(0)/(4pi)(m)/(2a^(2))`

Answer

B

Explanation

`B_(res)=2B" where "B=mu_(0)/(4pi)m/((a//sqrt3)^(2))`