JEE Main 2021 · PhysicsMultiple choiceSingle correctMediumCalculation

JEE Main 25 July 2021, Shift 2, Physics Q9

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

A heat engine has an efficiency of

\frac{1}{6}

. When the temperature of sink is reduced by 62°C, its efficiency get doubled. The temperature of the source is :

(1)37°C
(2)62°C
(3)99°COfficial answer
(4)124°C

Official answer

Option 3

NTA final key.

Chapter: Thermodynamics
Topic: Heat Engines and Refrigerators
Idea tested: Carnot Efficiency Limit

Same idea in other shifts

Asked 15× in all

8 Apr 2023, Shift 2 · Q34Work done by a Carnot engine operating between temperatures $127^\circ$ C and $27^\circ$ C is 2 kJ. The amount of heat transferred to the…EasySingle correct
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
25 Jul 2022, Shift 2 · Q45Let $\eta_1$ is the efficiency of an engine at $\mathrm{T_1}$ = 447°C and $\mathrm{T_2}$ = 147°C while $\eta_2$ is the efficiency at…EasySingle correct
28 Jul 2022, Shift 1 · Q37A Carnot engine has efficiency of 50%. If the temperature of sink is reduced by $40^\circ$ C, its efficiency increases by 30%. The…MediumSingle correct
30 Jul 2022, Shift 2 · Q7A Carnot engine is operating between the two reservoirs of temperature 227 $^\circ$ C and 127 $^\circ$ C respectively. If the engine…EasySingle correct
24 Jun 2022, Shift 1 · Q47A Carnot engine whose heat sinks at $27^\circ$ C, has an efficiency of 25%. By how many degrees should the temperature of the source be…MediumSingle correct
24 Jun 2022, Shift 2 · Q35A Carnot engine takes 5000 kcal of heat from a reservoir at $727^{\circ}C$ and gives heat to a sink at $127^{\circ}C$ . The work done by…EasySingle correct
26 Jun 2022, Shift 1 · Q37The efficiency of a Carnot's engine, working between steam point and ice point, will be :EasySingle 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.