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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceAssertion–reasonEasyConceptual

JEE Main 25 February 2021, Shift 1, Physics Q9

Question 9 of 90 in this shift, Physics question 9 of 30, Section A.

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R. Assertion A : When a rod lying freely is heated, no thermal stress is developed in it. Reason R : On heating, the length of the rod increases. In the light of the above statements, choose the correct answer from the options given below :
  1. (1)Both A and R are true and R is the correct explanation of A
  2. (2)Both A and R are true but R is NOT the correct explanation of AOfficial answer
  3. (3)A is true but R is false
  4. (4)A is false but R is true

Official answer

Option 2

NTA final key.

Chapter
Thermal Properties of Matter
Topic
Thermal Expansion
Idea tested
Thermal Stress

Same idea in other shifts

Asked 4× in all
  1. 8 Apr 2023, Shift 2 · Q52A steel rod of length 1 m and cross sectional area 10−410^{-4} m2^2 is heated from 0∘0^\circC to 200∘200^\circC without being allowed to…EasyNumerical value
  2. 4 Aug 2021, Shift 1 · Q16A steel wire of 1 mm2^2 cross-sectional area having Young’s modulus 2×10112\times10^{11} N/m2^2 is stretched between two fixed points at a…EasySingle correct
  3. 2 Apr 2017 (offline) · Q9An external pressure P is applied on a cube at 0°C so that it is equally compressed from all sides. K is the bulk modulus of the material…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.