Q.
Three infinite straight wires $A,\ B\ and\ C$ carry currents as shown. The net force on the wire $B$ is directed
A) Toward $A$
B) Toward $C$
C) Normal to plane of paper
D) zero
Explanation
(a) Force on wire $B\ due\ to\ A,$
$F_{BA} = \frac{\mu_{0} \times 1 \times 2}{2\pi r} = \frac{\mu_{0}}{\pi r}\ towards\ C$
Force on wire $B\ due\ to\ \ C$
$\ F_{BC} =$ $\frac{\mu_{0} \times 2 \times 3}{2\pi r} = \frac{{3\mu}_{0}}{\pi r}\ towards\ \ A$
Clearly $F_{BC} > F_{BA}$ therefore force on $B$ is directed towards $A$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.