Q. A chare $q$ coulomb moves in a circle at $n$ revolutions per second and the radius of the circle is $r$metre. Then the magnetic field at the centre of the circle is
A) $\frac{2\pi q}{nr} \times 10^{- 7}\ NA^{- 1}\ m^{- 1}$
B) $\frac{2\pi q}{r} \times 10^{- 7}\ NA^{- 1}\ m^{- 1}$
C) $\frac{2\pi nq}{r} \times 10^{- 7}\ NA^{- 1}\ m^{- 1}$
D) $\frac{2\pi q}{r} \times 10^{- 6}\ NA^{- 1}\ m^{- 1}$
Explanation
(c) Magnetic field at the centre of the circle
$B = \frac{\mu_{0}i}{2r}\ or\ B = \frac{\mu_{0}q}{2rT}$
$B = \frac{4\pi \times 10^{- 7} \times q}{2r}\ n$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.