Q. Two straight parallel wires, both carrying $10\ ampere$ in the same direction attract each other with a force of $1 \times 10^{- 3}N$. If both currents are doubled, the force of attraction will be
A) $1 \times 10^{- 3}N$
B) $2 \times 10^{- 3}N$
C) $4 \times 10^{- 3}N$
D) $0.25 \times 10^{- 3}N$
Explanation
(c) $F = \frac{\mu_{0}}{4\pi}\frac{2i_{1}i_{2}}{a} = 10^{- 3}N$
When current in both the wires is doubled, then
$F^{'} = \frac{\mu_{0}}{4\pi}\frac{2(2i_{1} \times 2i_{2})}{a} = 4 \times 10^{- 3}N$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.