Question

A charged particle of mass m and charge q is projected into a uniform magnetic field of induction B with speed v which is perpendicular to B. The width of the magnetic field is d. The impulse imparted to the particle by the field is (d <<):

• A. qBv
• B.
• C. qBd
• D.

Answer 1

Answer: (C)

qBd

Answer 2

As d < < < d = r sin q

Impulse is change in momentum

sin q = $\frac { \mathrm { d } } { \mathrm { r } }$ where r =

\ d < < < r \ sin q = q q =

Change in momentum = mv q = mv × $\frac { \mathrm { d } } { \mathrm { r } }$ = $\frac { \mathrm { mv } \times \mathrm { d } \times \mathrm { qB } } { \mathrm { mv } }$

Impulse = qBd