Question

The moment of magnet is $ 0.1\text{ }A{{m}^{2}} $ and the force acting on each pole in a uniform magnetic field of 0.36 oersted is $ 1.44\times {{10}^{-4}}N $ . The distance between the poles of magnet is

• A. 2.5 cm
• B. 5.0 cm
• C. 1.25cm
• D. 1.17cm

Answer 1

Answer: (A)

Here, $ M=0.1\text{ }A{{m}^{2}}, $ $ B=0.36 $ forested $ =0.36\times {{10}^{-4}}J, $ $ F=1.44\times {{10}^{-4}}N $ As $ F=mB $ $ \therefore $ $ m=\frac{F}{B}=\frac{1.44\times {{10}^{-4}}}{0.36\times {{10}^{-4}}}=4\,Am $ As $ M=m\times 2l $ $ \therefore $ $ 2l=\frac{M}{m}=\frac{0.1}{4}m=2.5\,m $