Q. The magnetic induction at the centre of a current carrying circular of radius $r,$ is
A) Directly proportional to $r$
B) Inversely proportional to $r$
C) Directly proportional to $r^{2}$
D) Inversely proportional to $r^{2}$
Explanation
(b) Magnetic field $(B)$ at the centre of a coil of radius $r,$ having $N$ turns carrying current $i$ is given by
$B = \frac{\mu_{0}Ni}{2r}\ {NA}^{- 1}m^{- 1}$
The direction of magnetic field is perpendicular to the plane of the coil, that is, along the axis of the coil. Hence, magnetic field is inversely proportional to $r.$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.