An inventor claims to have a heat engine that has efficiency of 40% when it operates between a high temperature reservoir of 150°C and a low temperature reservoir of 30°C.This engine:
A)must violate the zeroth law of thermodynamics
B)must violate the first law of thermodynamics
C)must violate the second law of thermodynamics
D)must violate the third law of thermodynamics
E)does not necessarily violate any of the laws of thermodynamics

Question

Quizplus · Accepted Answer

The second law of thermodynamics states that no engine can be more efficient than a Carnot engine operating between the same two reservoirs. The maximum efficiency of a Carnot engine operating between 150F1F1F1S1F1F1F10C and 30F1F1F1S1F1F1F10C is given by:
Efficiency = 1 - (T_low / T_high)
where T_low and T_high are the absolute temperatures of the low and high temperature reservoirs, respectively. Plugging in the values, we get:
Efficiency = 1 - (303 K / 394 K) = 0.233
Since the claimed efficiency of the engine is higher than the maximum efficiency of a Carnot engine operating between the same two reservoirs, it must violate the second law of thermodynamics.

An Inventor Claims to Have a Heat Engine That Has