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 magnetisation in $A / m$ will be

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

Answer 1

Answer: (A)

Intensity of magnetisation,
$I=\frac{M}{V}=\frac{M}{\text { mass } / \text { density }}$
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, $I=\frac{6 \times 10^{-7} \times 5 \times 10^{3}}{10^{-3}}$
$=3\, A / m$