JEE Main 2021 · PhysicsMultiple choiceSingle correctMediumApplication

JEE Main 18 March 2021, Shift 2, Physics Q16

Question 16 of 90 in this shift, Physics question 16 of 30, Section A.

A proton and an

\alpha

-particle, having kinetic energies

K_p

and

K_\alpha

respectively, enter into a magnetic field at right angles. The ratio of the radii of trajectory of proton to that of

\alpha

-particle is 2 : 1. The ratio of

K_p : K_\alpha

is :

(1) $1:4$
(2) $4:1$ Official answer
(3) $8:1$
(4) $1:8$

Official answer

Option 2

NTA final key.

Chapter: Moving Charges and Magnetism
Topic: Lorentz Force
Idea tested: Circular Motion in Uniform B-Field

Same idea in other shifts

Asked 7× in all

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Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.