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Saturday, 31 October

JEE Main · Physics · Thermodynamics

Carnot Efficiency Limit

JEE Main asked Carnot Efficiency Limit 15 times in 15 of the 108 shifts Lumi analysed, in 2021, 2022 and 2023. It belongs to Heat Engines and Refrigerators, in Thermodynamics (Physics). The longest wait between two years asking it was 1 year. In 2021, 2022 and 2023 it came in more than one shift of the same year.

Updated 2026-10-24

Times asked
15
in 15 shifts
Years
3 of 8
First asked
2021
last in 2023
Pattern
Comes in cycles
across the analysed shifts

Questions on this idea a shift, by year

2017–2026. Asked in 2021, 2022 and 2023. Years differ in how many shifts Lumi analysed, so each year is scaled to one shift of 25 Physics questions.

00.150.30’170’200.24’210.21’220.14’230’240’250’26

Raw count: 2017: 0 in 1 shift · 2020: 0 in 12 shifts · 2021: 7 in 24 shifts · 2022: 6 in 24 shifts · 2023: 2 in 12 shifts · 2024: 0 in 18 shifts · 2025: 0 in 8 shifts · 2026: 0 in 9 shifts.

Shift by shift

Each square is one analysed shift, in date order. Open a filled one for that paper.

  • 20260 of 9
  • 20250 of 8
  • 20240 of 18
  • 20232 of 12
  • 20226 of 24
  • 20217 of 24
  • 20200 of 12
  • 20170 of 1

Asked in that shift More than once Not asked

How JEE Main framed it

Single correct is the usual form. Skill tested: calculation.

  • Sink temperature from efficiency
  • Heat input from carnot work and temperatures

Difficulty

Easy 9Medium 6Hard 0

3 of the 15 questions had a numerical answer.

Every question

All 15 questions

From the official JEE Main shift papers, newest first. Open one for the full question, the options and the official answer.

  1. 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
  2. 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
  3. 26 Jun 2022, Shift 1 · Q37The efficiency of a Carnot's engine, working between steam point and ice point, will be :EasySingle correct
  4. 24 Jun 2022, Shift 2 · Q35A Carnot engine takes 5000 kcal of heat from a reservoir at 727∘C727^{\circ}C and gives heat to a sink at 127∘C127^{\circ}C. The work done by…EasySingle correct
  5. 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
  6. 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
  7. 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
  8. 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
  9. 17 Mar 2021, Shift 1 · Q3A Carnot's engine working between 400 K and 800 K has a work output of 1200 J per cycle. The amount of heat energy supplied to the engine…EasySingle correct
  10. 16 Mar 2021, Shift 2 · Q26For an ideal heat engine, the temperature of the source is 127∘127^\circC. In order to have 60% efficiency the temperature of the sink…EasyNumerical value
  11. 25 Jul 2021, Shift 2 · Q9A heat engine has an efficiency of 16\frac{1}{6}. When the temperature of sink is reduced by 62°C, its efficiency get doubled. The…MediumSingle correct
  12. 25 Feb 2021, Shift 2 · Q25A reversible heat engine converts one-fourth of the heat input into work. When the temperature of the sink is reduced by 52 K, its…MediumNumerical value
  13. 31 Aug 2021, Shift 1 · Q15A reversible engine has an efficiency of 14\frac{1}{4}. If the temperature of the sink is reduced by 58∘58^\circC, its efficiency becomes…MediumSingle correct
  14. 27 Aug 2021, Shift 2 · Q26A heat engine operates between a cold reservoir at temperature T2=400T_2=400 K and a hot reservoir at temperature T1T_1. It takes 300 J of…EasyNumerical value
  15. 3 Aug 2021, Shift 1 · Q5A carnot engine working at source temperature 400 KK, takes 500 JJ heat from the source and rejects 300 JJ to sink. What is the…EasySingle correct

Shifts: 25 Feb 2021, Shift 2, 16 Mar 2021, Shift 2, 17 Mar 2021, Shift 1, 25 Jul 2021, Shift 2, 3 Aug 2021, Shift 1, 27 Aug 2021, Shift 2, 31 Aug 2021, Shift 1, 24 Jun 2022, Shift 2, 24 Jun 2022, Shift 1, 26 Jun 2022, Shift 1, 25 Jul 2022, Shift 2, 28 Jul 2022, Shift 1, 30 Jul 2022, Shift 2, 8 Apr 2023, Shift 2, 12 Apr 2023, Shift 1.

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Other ideas in Heat Engines and Refrigerators

Heat Engines and Refrigerators has 8 ideas JEE Main has asked; 1 of them came up in more than one question.

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