Question

A small bar magnet has a magnetic moment $1.2\, Am ^{2}$. The magnetic field at a distance $0.1\, m$ on its axis will be $\left(\mu_{0}=4 \pi \times 10^{-7} T - m / A \right)$

• A. $1.2 \times 10^{-4} T$
• B. $2.4 \times 10^{-4} T$
• C. $2.4 \times 10^{4} T$
• D. $1.2 \times 10^{4} T$

Answer 1

Answer: (B)

$B=\frac{\mu_{0}}{4 \pi} \cdot \frac{2 M}{d^{3}}$
$\Rightarrow B=10^{-7} \times \frac{2 \times 1.2}{(0.1)^{3}}$
$=2.4 \times 10^{-4} T$