Question

The dipole moment of the short bar magnet is $12.5A-m^2$. The magnetic field on its axis at a distance of $0.5m$ from the centre of the magnet is

• A. $1.0\times {10}^{-4}N/A-m$
• B. $4\times {10}^{-2}N/A-m$
• C. $2\times {10}^{-6}N/A-m$
• D. $6.64\times {10}^{-8}N/A-m$

Answer 1

The correct option is C $2\times {10}^{-6}N/A-m$

The magnetic field, $B=\frac{{\mu }_0}{4\pi }\cdot \frac{2N}{d^3}$
$={10}^{-7}\times \frac{2\times 1.25}{{\left(0.5\right)}^3}=2\times {10}^{-6}N/A-m$