Question

Two parallel current carrying conductors carrying the same current 'I' in the same direction are seperated by a distance r. Force experienced per unit length by each conductor will be?

• A. Repulsive and $F=\frac{{\mu }_0{I}^2}{4\pi r}$
• B. Attractive and $F=\frac{{\mu }_{0}2I^2}{4\pi r}$
• C. Repulsive and $F=\frac{{\mu }_{0}2I^2}{4\pi r}$
• D. Attractive and $F=\frac{{\mu }_0{I}^2}{4\pi r}$

Answer 1

The correct option is B Attractive and $F=\frac{{\mu }_{0}2I^2}{4\pi r}$

The magnetic field at one of the wires due to the other is:
$B=\frac{2\mu I}{4\pi r}$
Therefore, the force per unit length experienced by the wire will be
$F=BI=\frac{2\mu I^2}{4\pi r}$
Also when the current is in the same direction then the force between the wires will be attractive in nature.