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Saturday, 31 October

JEE Main 2024 · PhysicsMultiple choiceSingle correctMediumMulti-step

JEE Main 30 January 2024, Shift 2, Physics Q40

Question 40 of 90 in this shift, Physics question 10 of 30, Section A.

A particle of charge '−q-q' and mass 'mm' moves in a circle of radius 'rr' around an infinitely long line charge of linear charge density '+λ+\lambda'. Then time period will be given as : (Consider kk as Coulomb's constant)
  1. (1)T=2πrm2kλqT = 2\pi r\sqrt{\frac{m}{2k\lambda q}}Official answer
  2. (2)T2=4π2m2kλqr3T^2 = \frac{4\pi^2 m}{2k\lambda q} r^3
  3. (3)T=12π2kλqmT = \frac{1}{2\pi}\sqrt{\frac{2k\lambda q}{m}}
  4. (4)T=12πrm2kλqT = \frac{1}{2\pi r}\sqrt{\frac{m}{2k\lambda q}}

Official answer

Option 1

NTA final key.

Chapter
Electrostatic Potential and Capacitance
Topic
Gauss's Law
Idea tested
Cylindrical Field

Same idea in other shifts

Asked 5× in all
  1. 4 Apr 2024, Shift 1 · Q40An infinitely long positively charged straight thread has a linear charge density λ\lambda Cm−1^{-1}. An electron revolves along a…HardDiagram basedHas a figure
  2. 10 Apr 2023, Shift 2 · Q55An electron revolves around an infinite cylindrical wire having uniform linear charge density 2×10−82\times10^{-8} C m−1^{-1} in circular path…MediumNumerical valueHas a figure
  3. 27 Jul 2022, Shift 1 · Q56A long cylindrical volume contains a uniformly distributed charge of density ρ\rho Cm−3^{-3}. The electric field inside the cylindrical…EasyNumerical valueHas a figure
  4. 24 Jun 2022, Shift 2 · Q46A long cylindrical volume contains a uniformly distributed charge of density ρ\rho. The radius of cylindrical volume is RR. A charge…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. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.