Question

The magnetic induction field strength due to a short bar magnet at a distance 0.20 m on the equatorial line is 20x10${}^{-6}$ tesla. The magnetic moment of the bar magnet is

• A. 3.2A.m${}^2$
• B. 6.4A.m${}^2$
• C. 1.6A.m${}^2$
• D. 16A.m${}^2$

Answer 1

The correct option is C 1.6A.m${}^2$

Magnetic field at the equator is,
B(equatorial) $=\frac{-{\mu }_{0}m}{4\pi d^3}$
$20\times {15}^6=\frac{2\times 4\pi \times {10}^{-7}\times m}{4\pi \times (0.2{)}^3}$
$m=1.6Am.$