Question

If $r$ be the distance of a point on the axis of a bar magnet from its center, the magnetic field at this point is proportional to

• A. $\left(1/r\right)$
• B. $\left(1/r^2\right)$
• C. $\left(1/r^3\right)$
• D. $\left(1/r^4\right)$

Answer 1

The correct option is C $\left(1/r^3\right)$

Using the relation,

$B=\frac{{\mu }_0\left(2M\right)}{4\pi d^3}$

$B=\frac{{\mu }_{0}M}{4\pi 4r^3}$

$B\propto \frac{1}{r^3}$

B= magnetic field

M= magnetic moment

r= distance.