Q. The helium nucleus makes a full rotation in a circle of radius 0.8 m in 2 s. The value of the magnetic field induction $B$ in tesla at the centre of circle will be
A) $2\ \times 10^{- 19}\ \mu_{0}$
B) $10^{- 19}/\mu_{0}$
C) $10^{- 19}\ \mu_{0}$
D) $2\ \times 10^{- 20}/\mu_{0}$
Explanation
(c) $B = \frac{\mu_{0}}{4\pi}\frac{2\pi i}{R}$
Where $i = \frac{2e}{t} = \frac{2 \times 1.6 \times 10^{- 19}}{2} = 1.6 \times 10^{- 19}$ A
$\therefore\ B = \frac{\mu_{0}i}{t} = \frac{\mu_{0} \times 1.6\ \times 10^{- 19}}{2 \times 0.8}$
$= \ \mu_{0} \times 10^{- 19}$ T
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.