Question

A rod of ferromagnetic material with dimensions $10cm\times 0.5cm\times 0.2cm$ is placed in a magnetic field of strength $0.5\times 10^{4}Am^{- 1}$ as a result of which a magnetic moment of $5Am^{2}$ is produced in the rod. The value of magnetic induction will be :-

• A. $0.54T$
• B. $6.28T$
• C. $0.358T$
• D. $2.591T$

Answer 1

Answer: (B)

Volume of $=10\times 0.5\times 0.2\times 10^{- 6}=10^{- 6}m^{3}$
$H=0.5\times 10^{4}Am^{- 1},M=5Am^{2}B=?$
Intensity of magnetisation i.e.
$I=\frac{M}{V}=\frac{5}{10^{- 6}}=5\times 10^{6}Am$
From $B=\left(\mu \right)_{0}\left(I + H\right)$
Magnetic induction
i.e. $B=4\pi \times 10^{- 7}\left[5 \times 10^{6} + 0 . 5 \times 10^{4}\right]$
$=4\pi \times 10^{- 7}\times 5\times 10^{6}=20\times 3.14\times 10^{- 1}$
$=6.28T$