Question

The length of a magnet of moment 5A-m${}^2$ is 14 cm. The magnetic induction at a point, equidistant from both the poles is $3.2\times {10}^{-5}$ Wb/m${}^2$. The distance of the point from either pole is :

• A. 25 cm
• B. 10 cm
• C. 15 cm
• D. 5 cm

Answer 1

The correct option is A 25 cm

Magnetic induction due to a dipole is given by:
$I=\frac{{\mu }_{o}m}{4\pi d^3}$

$\Rightarrow \frac{4\pi \times {10}^{-7}\times 5}{4\pi \times d^3}=3.2\times {10}^{-5}$

$d=0.25m$

$d=25cm$.