Question

The magnetic induction field strength due to a short bar magnet at a distance $0.20 \, m$ on the equatorial line is $20\times 10^{- 6} \, T$ . The magnetic moment of the bar magnet is

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

Answer 1

Answer: (C)

$B=\frac{\mu _{0}}{4 \pi }\frac{M}{d^{3}}$
$20\times 10^{- 6}=\frac{10^{- 7} \times M}{8 \times 10^{- 3}}$
$M=\frac{1.6 \times 10^{- 7}}{10^{- 7}}=1.6 \, A \, m^{2}$