Learn

Saturday, 31 October

JEE Main 2020 · PhysicsMultiple choiceDiagram basedMediumCalculation

JEE Main 2 September 2020, Shift 2, Physics Q12

Question 12 of 75 in this shift, Physics question 12 of 25.

The figure shows a region of length ‘ll’ with a uniform magnetic field of 0.3 T in it and a proton entering the region with velocity 4×\times105^5 ms−1^{-1} making an angle 60° with the field. If the proton completes 10 revolution by the time it cross the region shown, ‘ll’ is close to (mass of proton = 1.67×\times10−27^{-27} kg, charge of the proton=1.6×\times10−19^{-19} C)

The figure, in words

Region bounded by two vertical lines, with five parallel horizontal arrows pointing right inside it, labelled B above. The width between the two vertical lines is marked l (two arrows with dashed ticks pointing in from outside at the bottom). On the left, an arrow enters the region from the left side, drawn at an angle labelled 60° to a dashed horizontal line.
  1. (1)0.88 m
  2. (2)0.44 mOfficial answer
  3. (3)0.22 m
  4. (4)0.11 m

Official answer

Option 2

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 7× 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
  2. 4 Apr 2024, Shift 1 · Q42An electron is projected with uniform velocity along the axis inside a current carrying long solenoid. Then :EasySingle correct
  3. 6 Apr 2023, Shift 2 · Q57A proton with a kinetic energy of 2.0 eV moves into a region of uniform magnetic field of magnitude π2×10−3\frac{\pi}{2}\times10^{-3} T. The…MediumNumerical value
  4. 8 Apr 2023, Shift 1 · Q48A charge particle moving in magnetic field B, has the components of velocity along B as well as perpendicular to B. The path of the charge…EasySingle correct
  5. 11 Apr 2023, Shift 2 · Q48An electron is allowed to move with constant velocity along the axis of current carrying straight solenoid. A. The electron will…MediumOther
  6. 2 Sep 2020, Shift 1 · Q13A 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…MediumSingle 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. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.