Question

A rectangular loop ABCD, carrying a current 15 A, is placed near a long wire carrying a current 40 A. The resultant force acting on the loop is

• A. $6.4\times {10}^{-2}N$ directed away from wire
• B. $6.4\times {10}^{-2}N$ directed towards wire
• C. $3.6\times {10}^{-2}N$ directed away from wire
• D. $3.6\times {10}^{-2}N$ directed towards the wire

Answer 1

The correct option is D

$3.6\times {10}^{-2}N$ directed towards the wire

$F=\frac{{\mu }_0{i}_1{i}_{2}l}{2\pi }(\frac{1}{r_1}-\frac{1}{r_2})=\frac{4\pi \times {10}^{-7}\times 40\times 15\times 3}{2\pi }(\frac{1}{0.01}-\frac{1}{0.81})=3.6\times {10}^{-2}N$
This will act towards the long wire.