Q. Two parallel wires in free space are $10\ cm$ apart and each carries a current of $10\ A$ in the same direction. The force one wire exerts on the other per metre of length is
A) $2 \times 10^{- 4}N$, attractive
B) $2 \times 10^{- 4}N$, repulsive
C) $2 \times 10^{- 7}N$, attractive
D) $2 \times 10^{- 7}N$, repulsive
Explanation
(a) $F = \frac{\mu_{0}}{4\pi}\frac{2i_{1}i_{2}}{a} = 10^{- 7} \times \frac{2 \times 10 \times 10}{0.1} = 2 \times 10^{- 4}N$
Direction of current is same, so force is attractive
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.