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Friday, 9 October

JEE Main 2020 · PhysicsMultiple choiceSingle correctMediumCalculation

JEE Main 2 September 2020, Shift 1, Physics Q13

Question 13 of 75 in this shift, Physics question 13 of 25.

A beam of protons with speed 4×105 ms−14\times10^{5}\ \mathrm{ms^{-1}} enters a uniform magnetic field of 0.3 T at an angle of 60∘60^\circ to the magnetic field. The pitch of the resulting helical path of protons is close to : (Mass of the proton =1.67×10−27=1.67\times10^{-27} kg, charge of the proton =1.69×10−19=1.69\times10^{-19} C)
  1. (1)2 cm
  2. (2)5 cm
  3. (3)4 cmOfficial answer
  4. (4)12 cm

Official answer

Option 3

NTA final key (Sep 2020).

Chapter
Moving Charges and Magnetism
Topic
Lorentz Force
Idea tested
Helical Motion and Pitch

Same idea in other shifts

Asked 2× in all
  1. 8 Apr 2026, Shift 2 · Q48A 5 mg particle carrying a charge of 5π×10−65\pi \times 10^{-6} C is moving with velocity of (3i^+2k^)×10−2\left(3\hat{i} + 2\hat{k}\right) \times 10^{-2}…MediumNumerical value

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 42 of the 174 JEE Main shifts held from 2017 to 2026.