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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceSingle correctMediumCalculation

JEE Main 27 August 2021, Shift 1, Physics Q1

Question 1 of 90 in this shift, Physics question 1 of 30, Section A.

In Millikan’s oil drop experiment, what is viscous force acting on an uncharged drop of radius 2.0×10−52.0\times10^{-5} m and density 1.2×1031.2\times10^{3} kgm−3^{-3} ? Take viscosity of liquid =1.8×10−5=1.8\times10^{-5} Nsm−2^{-2}. (Neglect buoyancy due to air).
  1. (1)5.8×10−105.8\times10^{-10} N
  2. (2)1.8×10−101.8\times10^{-10} N
  3. (3)3.8×10−113.8\times10^{-11} N
  4. (4)3.9×10−103.9\times10^{-10} NOfficial answer

Official answer

Option 4

NTA final key.

Chapter
Moving Charges and Magnetism
Topic
Viscosity
Idea tested
Stokes' Law

Same topic in other shifts

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  6. 9 Apr 2024, Shift 2 · Q40A spherical ball of radius 1×10−41\times10^{-4} m and density 105 kg/m310^5\ \mathrm{kg/m^3} falls freely under gravity through a distance hh before…HardSingle 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.