Write an expression for the magnitude of the magnetic field at a point lying on the equatorial line of a bar magnet.

(N/A) The magnetic field $B$ at a point on the equatorial line of a bar magnet of magnetic dipole moment $M$ and length $2l$ at a distance $r$ from its center is given by:
$B = \frac{\mu_{0}}{4 \pi} \frac{M}{(r^{2} + l^{2})^{3/2}}$
For a short bar magnet where $r \gg l$,the expression simplifies to:
$B = \frac{\mu_{0} M}{4 \pi r^{3}}$
Where:
$\mu_{0} = \text{permeability of free space}$
$M = \text{magnetic dipole moment}$
$r = \text{perpendicular distance from the center of the magnet}$