Magnetics 1 Question 15

15. A proton, a deutron and an α-particle having the same kinetic energy are moving in circular trajectories in a constant magnetic field. If rp,rd and rα denote, respectively the radii of the trajectories of these particles, then

(1997, 1M)

(a) rα=rp<rd

(b) rα>rd>rp

(c) rα=rd>rp

(d) rp=rd=rα

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Answer:

Correct Answer: 15. (a)

Solution:

  1. Radius of the circular path is given by

r=mvBq=2KmBq

Here, K is the kinetic energy to the particle.

Therefore, rmq if K and B are same.

rp:rd:rα=11:21:42=1:2:1

Hence,

rα=rp<rd



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