A Carnot engine operates between 400 K and 300 K. Its efficiency is: MCQ with Answer and Explanation

A Carnot engine operates between 400 K and 300 K. Its efficiency is:
A. 25%
B. 20%
C. 33.3%
D. 75%
Answer: Option A
Solution (By JKSSB Mock Tests)
Carnot efficiency η = 1 - T₂/T₁, where T₁ is source temperature, T₂ sink temperature (in Kelvin). Here T₁=400 K, T₂=300 K, so η = 1 - 300/400 = 1 - 0.75 = 0.25 = 25%. This maximum possible efficiency for given temperatures is a fundamental thermodynamics result. Memory tip: 'η_Carnot = 1 - T_cold/T_hot'. Competitive exams frequently test this formula with varying temperatures. Always use absolute temperatures (Kelvin); Celsius would yield incorrect efficiency. This problem assesses understanding of heat engine limitations.

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Correct Answer: Option B


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Correct Answer: Option D


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A body of mass 5 kg moving with velocity 2 m/s collides with a stationary body of mass 3 kg and sticks to it. Combined velocity is
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Correct Answer: Option B


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