Question

The magnetic moment produced in a substance of $1 \,g$ is $6 \times 10^{-7} A^{-} m ^{2}$. If its density is $5 \,g / cm ^{3}$, then the intensity of magnetization in $A / m$ will be

• A. $ 8.3\times 10^{6}$
• B. $ 3.0 $
• C. $ 1.2\times 10^{-7} $
• D. $ 3\times 10^{-6} $

Answer 1

Answer: (B)

Intensity of magnetisation $I=\frac{M}{V}=\frac{M}{\text { mass/density }}$
Given mass $=1 g=10^{-3} kg$ and density
$=5 \,g / cm ^{3}=\frac{5 \times 10^{-3} kg }{\left(10^{-2}\right)^{3} m ^{3}}$
$=5 \times 10^{3} \,kg / m ^{3}$
Hence, $I=\frac{6 \times 10^{-7} \times 5 \times 10^{3}}{10^{-3}}$
$=3\, A / m$