Q18 / 160 · NTA Abhyas (JEE Main) 2020 · Physics · Thermodynamics

A Carnot engine whose sink is at 300 K has an efficiency of 40%. By how much should the temperature of source be increased so as to increase its efficiency by 50% of original efficiency?

Correct answer: 250

Solution

T2T1=1-η=1-40100=35

∴ T1=53T2=53×300=500K

Increase in efficiency =50% of 40%=20%

∴ New efficiency η′=40+20=60%

∴ T2T′1=1-η′=1-60100=25

T1′=52×300=750 K

Increase in temperature of source =T1′-T1

=750-500=250 K

Hence, the correct answer is 250.

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