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Saturday, 31 October

JEE Main 2022 · PhysicsMultiple choiceDiagram basedEasyConceptual

JEE Main 27 July 2022, Shift 2, Physics Q38

Question 38 of 90 in this shift, Physics question 8 of 30, Section A.

In 1st^{st} case, Carnot engine operates between temperatures 300 K and 100 K. In 2nd^{nd} case, as shown in the figure, a combination of two engines is used. The efficiency of this combination (in 2nd^{nd} case) will be :

The figure, in words

Vertical stack: reservoir 300 K, engine E1, reservoir 200 K, engine E1 (second engine also labelled E1 as printed), reservoir 100 K; labelled '2nd Case'.
  1. (1)same as the 1st^{st} case.Official answer
  2. (2)always greater than the 1st^{st} case.
  3. (3)always less than the 1st^{st} case.
  4. (4)may increase or decrease with respect to the 1st^{st} case.

Official answer

Option 1

NTA final key.

Chapter
Thermodynamics
Topic
Heat Engines and Refrigerators
Idea tested
Carnot Engines in Series

Same topic in other shifts

All Heat Engines and Refrigerators questions
  1. 8 Apr 2023, Shift 2 · Q34Work done by a Carnot engine operating between temperatures 127∘127^\circC and 27∘27^\circC is 2 kJ. The amount of heat transferred to the…EasySingle correct
  2. 12 Apr 2023, Shift 1 · Q38An engine operating between the boiling and freezing points of water will have A. efficiency more than 27%. B. efficiency less than the…MediumOther
  3. 25 Jul 2022, Shift 2 · Q45Let η1\eta_1 is the efficiency of an engine at T1\mathrm{T_1} = 447°C and T2\mathrm{T_2} = 147°C while η2\eta_2 is the efficiency at…EasySingle correct
  4. 28 Jul 2022, Shift 1 · Q37A Carnot engine has efficiency of 50%. If the temperature of sink is reduced by 40∘40^\circC, its efficiency increases by 30%. The…MediumSingle correct
  5. 30 Jul 2022, Shift 2 · Q7A Carnot engine is operating between the two reservoirs of temperature 227 ∘^\circC and 127 ∘^\circC respectively. If the engine…EasySingle correct
  6. 24 Jun 2022, Shift 1 · Q47A Carnot engine whose heat sinks at 27∘27^\circC, has an efficiency of 25%. By how many degrees should the temperature of the source be…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.