Question

Two long parallel wires seperated by 20 cm and carries currents in same direction, $i_1=2A$ & $i_2=4A$, find the force acting per unit length between wires ?

• A. $8\times {10}^{-6}N$
• B. $4\times {10}^{-6}N$
• C. $8\times {10}^{-3}N$
• D. $4\times {10}^{-3}N$

Answer 1

The correct option is A $8\times {10}^{-6}N$

$F=\frac{{\mu }_0}{2\pi }\frac{i_1{i}_2}{d}$
= $\frac{2\times {10}^{-7}\times 2\times 4}{20\times {10}^{-2}}$
$=\frac{2\times {10}^{-7}\times 8}{2\times {10}^{-1}}=8\times {10}^{-6}N$