A heat engine operates between 200 K and 100 K.In each cycle it takes 100 J from the hot reservoir, loses 25 J to the cold reservoir, and does 75 J of work.This heat engine violates:
A)both the first and second laws of thermodynamics
B)the first law but not the second law of thermodynamics
C)the second law but not the first law of thermodynamics
D)neither the first law nor the second law of thermodynamics
E)cannot answer without knowing the mechanical equivalent of heat

Question

Quizplus · Accepted Answer

According to the second law of thermodynamics, no heat engine can have a greater efficiency than a Carnot engine operating between the same two temperatures. The efficiency of a Carnot engine operating between 200 K and 100 K is 1 - (100/200) = 0.5 or 50%. The efficiency of this engine is (100-25)/100 = 75%, which is higher than the Carnot efficiency. Therefore, this engine violates the second law of thermodynamics. The first law of thermodynamics is not violated as the amount of energy input and output are accounted for.

A Heat Engine Operates Between 200 K and 100 K