Question

Two thin long parallel wires separated by a distance b are carrying a current i amp each. The magnitude of the force per unit length exerted by one wire on the other is

• A. $\frac{{\mu }_0{i}^2}{b^2}$
• B. $\frac{{\mu }_0{i}^2}{2\pi b}$
• C. $\frac{{\mu }_{0}i}{2\pi b}$
• D. $\frac{{\mu }_{0}i}{2\pi b^2}$

Answer 1

The correct option is B $\frac{{\mu }_0{i}^2}{2\pi b}$

Force per unit length $=\frac{{\mu }_0}{4\pi }.\frac{2i_1{i}_2}{r}=\frac{{\mu }_0}{2\pi }.\frac{i^2}{b}$