Question

A long wire A carries a current of 10 amp. Another long wire B, which is parallel to A and separated by 0.1 m from A, carries a current of 5 amp in the opposite direction to that in A. What is the magnitude and nature of the force experienced per unit length of B
$[{\mu }_0=4\pi \times {10}^{-7}weber/amp-m]$

• A. Repulsive force of ${10}^{-4}N/m$
  
• B. Attractive force of ${10}^{-4}N/m$
  
• C. Repulsive force of $2\pi \times {10}^{-5}N/m$
  
• D. Attractive force of $2\pi \times {10}^{-5}N/m$

Answer 1

The correct option is A Repulsive force of ${10}^{-4}N/m$


By using $\frac{F}{l}=\frac{{\mu }_0}{4\pi }.\frac{2i_1{i}_2}{a}$
$\Rightarrow$ $\frac{F}{l}={10}^{-7}\times \frac{2\times 10\times 5}{0.1}={10}^{-4}N$
Wires are carrying current in opposite direction so the force will be repulsive.