Q. A power line lies along the east-west direction and carries a current of $10\ ampere$. The force per metre due to the earth’s magnetic field of $10^{- 4}tesla$ is
A) $10^{- 5}N$
B) $10^{- 4}N$
C) $10^{- 3}N$
D) $10^{- 2}N$
Explanation
(c) Force on the wire $= Bil$
Force per unit length $= Bi = 10^{- 4} \times 10 = 10^{- 3}N$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.