Question

Two long straight wires are set parallel to each other Each carries a current $i$ in the opposite direction and the separation between them is 2R. The intensity of the magnetic field midway between them is

• A. zero
• B. $\frac{{\mu }_{0}i}{4\pi R}$
• C. $\frac{{\mu }_{0}i}{2\pi R}$
• D. $\frac{{\mu }_{0}i}{\pi R}$

Answer 1

Answer: (B)

Magnetic field at mid point due to wire AB
$B_1=\frac{{\mu }_{0}i}{2\pi R}$
Magnetic field at midpoint due to wire CD
$B_2=\frac{{\mu }_{0}i}{2\pi R}$
Resultant of Magnetic field
$B=B_1+B_2$
$=\frac{{\mu }_{0}i}{2\pi R}+\frac{{\mu }_{0}i}{2\pi R}$
$B=\frac{{\mu }_{0}i}{\pi R}$