Q. The strength of the magnetic field around a long straight wire, carrying current, is
A) Same everywhere around the wire at any distance
B) Inversely proportional to the distance from the wire
C) Inversely proportional to the square of the distance from the wire
D) Directly proportional to the square of the distance from the wire
Explanation
(b) The strength of magnetic field around a straight current carrying wire is given by
$B = \frac{\mu_{0}}{2\pi}\ .\frac{I}{r}$
$\therefore\ \ B \propto \frac{1}{r}$
Therefore, magnetic field due to a straight current carrying wire is inversely proportional to the distance from the wire.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.