Question

The magnetic moment of a short magnet is $8A{m}^2.$ The magnetic induction at appoint 20 cm away from its mid-point on (i) a axial point (ii) equatorial point respectively, will be :

• A. $2\times {10}^{-4}Tand{10}^{-4}T$
• B. $3\times {10}^{-4}Tand2\times {10}^{-4}T$
• C. $4\times {10}^{-4}Tand3\times {10}^{-4}T$
• D. none of these

Answer 1

Answer: (A)

Magnetic induction in axial position. $B_1=\frac{{\mu }_0}{4\pi }\frac{2M}{d^3}$ $={10}^{-7}\times \frac{2\times 8}{{(20\times {10}^{-2})}^2}$ $=\frac{{10}^{-7}\times 16}{8\times {10}^{-3}}=2\times {10}^{-4}T$ At equatorial position $B_2=\frac{B_1}{2}$ $=\frac{2\times {10}^{-4}}{2}={10}^{-4}T$