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PhysicsMagnetismMagnetic ForceMedium2 minPYQ_2020
PhysicsMediumsingle choice

A charged particle of mass ‘m’ and charge ‘q’ moving under the influence of uniform electric fieldE i^and a uniform magnetic fieldB k^follows a trajectory from point P to Q as shown in figure. The velocities at P and Q are respectively,viand-2vj. Then which of the following statements (A, B, C, D) are the correct? (Trajectory shown is schematic and not to scale)



AE=32mv2qa
BRate of work done by the electric field at P is32mv3a
CRate of work done by both the fields at Q is zero
DThe difference between the magnitude of angular momentum of the particle at P and Q is2mav.

Question diagram: A charged particle of mass ‘ m ’ and charge ‘ q ’ moving und

Options:

Answer:
C
Solution:

(A) by work energy theorem

Wmag+Wele=12m(2v)2-12m(v)2

0+qE02a=32mv2
E0=34mv2qa

(B) Rate of work done at A= power of electric force

=qE0V
=34mv3a

(C) at Q,dwdt=0 for both forces

D ΔL=(-m2 v 2ak^)-(- mvak )

|ΔL|=3mva

Stream:JEESubject:PhysicsTopic:MagnetismSubtopic:Magnetic Force
2mℹ️ Source: PYQ_2020

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