Q. Two long parallel wires $P$ and $Q$ are both perpendicular to the plane of the paper with distance $5\ m$ between them. If $P$ and $Q$ carry current of $2.5\ amp$ and $5\ amp$ respectively in the same direction, then the magnetic field at a point half way between the wires is
A) $\frac{\sqrt{3}\mu_{0}}{2\pi}$
B) $\frac{\mu_{0}}{\pi}$
C) $\frac{3\mu_{0}}{2\pi}$
D) $\frac{\mu_{0}}{2\pi}$
Explanation
(d) In the following figure magnetic field at mid point $M$ is given by
$B_{net} = B_{Q} - B_{P}$
$= \frac{\mu_{0}}{4\pi}.\frac{2}{r}(i_{Q} - i_{P})$
$= \frac{\mu_{0}}{4\pi} \times \frac{2}{2.5}(5 - 2.5) = \frac{\mu_{0}}{2\pi}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.