Q. A magnetic material of volume 30 cm³ is placed in a magnetic field of intensity 5 oersted. The magnetic moment produced due it is 6 amp – m². The value of magnetic induction will be.

(a) 0.2517 Tesla

(b) 0.025 Tesla

(c) 0.0025 Tesla

(d) 25 Tesla

Ans: (a)

Sol: $ \displaystyle H = \frac{5\times 10^3}{4 \pi} A/m$

H = 398 A/m

$ \displaystyle I = \frac{M}{V} $

$ \displaystyle I = \frac{ 6}{30 \times 10^{-6}} $

I = 0.2 × 10^{6}

$\displaystyle B = \mu_0 (H + I) $

$ \displaystyle B = 4 \pi \times 10^{-7} (398 + 2 \times 10^5) $

B = 0.2517 T