Question

A current of one ampere is passed through a straight wire of length 2 metre. The magnetic field at a point in air at a distance of 3 m from one end of the wire but lying on the axis of the wire will be

• A. ${\mu }_0/2\pi$
• B. ${\mu }_0/4\pi$
• C. ${\mu }_0/8\pi$
• D. Zero

Answer 1

Answer: (D)

$B=\frac{{\mu }_{0}i}{2\pi r}$