Question

A short bar magnet has magnetic moment of $50 Am ^{2}$. Calculate the magnetic field intensity at a distance of $0.2 m$ from its centre on axial line.

• A. $1.5 \times 10^{-4} T$
• B. $1.25 \times 10^{-4} T$
• C. $1.5 \times 10^{-3} T$
• D. $1.25 \times 10^{-3} T$

Answer 1

Answer: (D)

As we know,
$B=\frac{\mu_{0} 2 M}{4 \pi r^{3}}$
$=\frac{10^{-7} \times 2 \times 50}{(0.2)^{3}}$
$=\frac{10^{-7} \times 100}{8 \times 10^{-3}}$
$B =1.25 \times 10^{-3} T$