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Class 12 › Physics › Moving Charges and Magnetism
CBSE2020Class Class 12 · Physics2 Marks · Short✅ Verified
Derive the expression for radius $r$ of the circular path of an electron moving in a perpendicular uniform magnetic field $B$.
✅ Answer & Solution
For circular motion, magnetic force = centripetal force:
$$qvB = \frac{mv^2}{r}$$
$$r = \frac{mv}{qB}$$
For an electron ($q = e$):
$$r = \frac{mv}{eB}$$
where $m$ = mass of electron, $v$ = speed, $e$ = charge of electron, $B$ = magnetic field.
