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Saturday, 31 October

JEE Main 2024 · PhysicsMultiple choiceDiagram basedHardData or graph

JEE Main 4 April 2024, Shift 1, Physics Q40

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

An infinitely long positively charged straight thread has a linear charge density λ\lambda Cm−1^{-1}. An electron revolves along a circular path having axis along the length of the wire. The graph that correctly represents the variation of the kinetic energy of electron as a function of radius of circular path from the wire is :

The figure, in words

Four KE-vs-r graphs (axes KE vertical, r horizontal, origin O) as options.
  1. (1)[figure: graph of KE vs r, decreasing convex curve falling from high KE toward the r-axis]
  2. (2)[figure: graph of KE vs r, curve from origin O increasing with increasing slope (convex upward)]
  3. (3)[figure: graph of KE vs r, straight line through origin O with positive slope]
  4. (4)[figure: graph of KE vs r, horizontal straight line at constant KE]Official answer

Official answer

Option 4

NTA final key.

Chapter
Electric Charges and Fields
Topic
Gauss's Law
Idea tested
Cylindrical Field

Same idea in other shifts

Asked 5× in all
  1. 30 Jan 2024, Shift 2 · Q40A particle of charge '−q-q' and mass 'mm' moves in a circle of radius 'rr' around an infinitely long line charge of linear charge…MediumSingle correct
  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. 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.