Question

Two parallel wires $1m$ apart carry currents of $1A$ and $3A$ respectively in opposite directions. The force per unit length acting between these two wires is

• A. $6\times {10}^{-7}N{m}^{-1}repulsive$
• B. $6\times {10}^{-7}N{m}^{-1}attractive$
• C. $6\times {10}^{-5}N{m}^{-1}repulsive$
• D. $6\times {10}^{-5}N{m}^{-1}attractive$

Answer 1

The correct option is A $6\times {10}^{-7}N{m}^{-1}repulsive$

Given : $I_1=1$ A $I_2=3$ A $d=1$ m

Force between two wires having respective current flowing in opposite direction is repulsive in nature.

Force per unit length, $f=\frac{{\mu }_o}{4\pi }.\frac{2I_1{I}_2}{d}$

$\therefore$ $f={10}^{-7}\times \frac{2\left(1\right)\left(3\right)}{1}=6\times {10}^{-7}$ $N/m$ (repulsive)