Question

Two long parallel current carrying wires are separated by 5 cm in air and are carrying current of 40A in the opposite direction. The force per meter length between the wires will be .

• A. $-6.4\times {10}^{-3}N$
• B. $6.4\times {10}^{-3}N$
• C. $-3.2\times {10}^{-3}N$
• D. $3.2\times {10}^{-3}N$

Answer 1

The correct option is A $-6.4\times {10}^{-3}N$

The expression for force per meter length is,

$F=\frac{{\mu }_0{I}_1{I}_2}{2\pi D}$

Where, $I_1=I_2=40A$

distance , $D=5\times {10}^{-2}$

$F=2\times {10}^{-7}\times \frac{40\times 40}{5\times {10}^{-2}}$

$F=6.4\times {10}^{-3}N$

The direction of force will be repulsive in nature ,

Then , $F=-6.4\times {10}^{-3}N$