question_answer

The distance between the poles of a horse shoe magnet is 0.1 m and its pole strength is 0.01 amp-m. The induction of magnetic field at a  point midway between the poles will be

A) \[2\times {{10}^{-5}}\,T\]        

B) \[4\times {{10}^{-6}}\,T\]

C) \[8\times {{10}^{-7}}\,T\]                    

D) zero

Correct Answer: C

Solution :

Net magnetic field at midpoint \[P,\,\,B={{B}_{N}}\,+\,{{B}_{S}}\] \[where\,\,{{B}_{N}}=magnetic\,\,field\,\,due\,\,to\,\,N-pole\] \[{{B}_{S}}=magnetic\text{ }field\text{ }due\text{ }to\text{ }S-pole\] \[=\,\,{{10}^{-7}}\,\times \,\,\frac{0.01}{{{\left( \frac{0.1}{2} \right)}^{2}}}\] \[=\,\,4\times {{10}^{-7}}\,T\] \[\therefore \,\,\,\,{{B}_{net}}\,=\,8\times {{10}^{-7}}\,T\]