Question

Two infinitely long parallel wires carrying current of 3A and 5A placed in the same plane at a distance of 2 m. The magnetic forces on 5 cm segment of wire A is:

• A. $1.5\times {10}^{-8}N$
• B. $7.5\times {10}^{-8}N$
• C. $3\times {10}^{-5}N$
• D. zero

Answer 1

The correct option is B $7.5\times {10}^{-8}N$

$\text{Given}:$ $I_1=3A,I_2=5A,l=0.05m,r=2m$

$\text{Solution}:$

We know that the force between two infintely long wire is given by,

$F=\frac{{\mu }_o}{4\pi }\times \frac{2I_1{I}_2}{r}\times l$

$={10}^{-7}\times \frac{2\times 5\times 3\times 0\cdot 05}{(2\cdot 0)}$

=$7.5\times {10}^{-8}N$

$\text{Hence B is the correct option}$