Question

The force per unit length between two parallel current carrying straight conductors separated by $2d$ is given by the formula

• A. $\frac{\mu_{0}}{4 \pi} \frac{i_{1} i_{2}}{d}$
• B. $\frac{\mu_{0}}{4 \pi} \frac{i_{1} i_{2}}{2 d}$
• C. $\frac{\mu_{0}}{\pi} \frac{i_{1} i_{2}}{2 d}$
• D. None of these

Answer 1

Answer: (A)

Force per unit length between the two parallel current carrying wires

$\frac{F}{L}=\frac{\mu_{0}}{2 \pi r} i_{1} i_{2}$
$=\frac{\mu_{0}}{2 \pi(2 d)} i_{1} i_{2}=\frac{\mu_{0} i_{1} i_{2}}{4 \pi d}[\because r=2 d]$