JEE Main 2021 · PhysicsMultiple choiceSingle correctMediumApplication

JEE Main 25 February 2021, Shift 1, Physics Q15

Question 15 of 90 in this shift, Physics question 15 of 30, Section A.

A proton, a deuteron and an

\alpha

particle are moving with same momentum in a uniform magnetic field. The ratio of magnetic forces acting on them is __________ and their speed is __________, in the ratio.

(1)4 : 2 : 1 and 2 : 1 : 1
(2)2 : 1 : 1 and 4 : 2 : 1Official answer
(3)1 : 2 : 4 and 1 : 1 : 2
(4)1 : 2 : 4 and 2 : 1 : 1

Official answer

Option 2

NTA final key.

Chapter: Moving Charges and Magnetism
Topic: Lorentz Force
Idea tested: Magnetic Force Vector Calculation

Same idea in other shifts

Asked 7× in all

2 Apr 2026, Shift 1 · Q48 $1\ \mu$ C charge moving with velocity $\vec v=\left(\hat i-2\hat j+3\hat k\right)$ m/s in the region of magnetic field…EasyNumerical value
5 Apr 2026, Shift 1 · Q49The charged particle moving in a uniform magnetic field of $(3\hat{i} + 2\hat{j})\,\mathrm{T}$ has an acceleration…MediumNumerical value
26 Jul 2022, Shift 1 · Q38A charge particle is moving in a uniform magnetic field $\left(2\hat{i} + 3\hat{j}\right)$ T. If it has an acceleration of…EasySingle correct
28 Jul 2022, Shift 2 · Q12A triangular shaped wire carrying 10 A current is placed in a uniform magnetic field of 0.5 T, as shown in figure. The magnetic force on…EasySingle correctHas a figure
8 Jan 2020, Shift 1 · Q12Proton with kinetic energy of 1 MeV moves from south to north. It gets an acceleration of $10^{12}$ m/s $^2$ by an applied magnetic field…MediumSingle correct
3 Sep 2020, Shift 1 · Q2A charged particle carrying charge 1 $\mu$ C is moving with velocity $(2\hat{i} + 3\hat{j} + 4\hat{k})$ ms $^{-1}$ . If an external magnetic…EasySingle correct

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.