Question

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. $\frac{{\mu }_0}{2\pi }$

Answer 1

The correct option is D $\frac{{\mu }_0}{2\pi }$

In the following figure magnetic field at mid point M is given by
$B_{net}=B_Q-B_P$
$=\frac{{\mu }_0}{4\pi }.\frac{2}{r}(i_Q-i_P)$
$=\frac{{\mu }_0}{4\pi }\times \frac{2}{2.5}(5-2.5)=\frac{{\mu }_0}{2\pi }$