Question

A bar magnet has length $3cm$, cross-sectional area $2c{m}^2$ and magnetic moment $3A{m}^2$. The intensity of magnetisation of bar magnet is

• A. $2\times 10^{5}A/m$
• B. $3\times 10^{5}A/m$
• C. $4\times 10^{5}A/m$
• D. $5\times 10^{5}A/m$

Answer 1

Answer: (D)

Length of the bar magnet $L=3cm=3\times 10^{-2}m$
Area of bar magnet $A=2c{m}^2=2\times 10^{-4}{m}^2$
Thus volume of bar magnet $V=AL$
$\therefore V=3\times 10^{-2}\times 3\times 10^{-4}=6\times 10^{-6}{m}^3$
Magnetic moment $\mu =3A{m}^2$
Thus intensity of magnetisation $I=\frac{\mu }{V}$
$\therefore I=\frac{3}{6\times 10^{-6}}=5\times 10^{5}A/m$