Q. A wire carrying current $I$ and other carrying $2I$ in the same direction produces a magnetic field $B$ at the mid point. What will be the field when $2I$ wire is switched off
A) $B/2$
B) $2B$
C) $B$
D) $4B$
Explanation
(c) When two parallel conductors are carrying current $I$ and $2I$ in same direction, then magnetic field at the midpoint is
$B = \frac{\mu_{0}2l}{2\pi r} - \frac{\mu_{0}I}{2\pi r} = \frac{\mu_{0}I}{2\pi r}$
When current $2I$ is switched off then magnetic field due to conductor carrying current $I$ is $B = \frac{\mu_{0}I}{2\pi r}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.