An ideal frictionless engine takes in 10 kJ of heat per second when it operates between 500 K and 400 K. The work that the engine does per second is
A) 2 kJ.
B) 2.5 kJ.
C) 8 kJ.
D) 10 kJ.

Question

Quizplus · Accepted Answer

The efficiency of an ideal engine is given by 1 - T_c/T_h, where T_c is the cold reservoir temperature and T_h is the hot reservoir temperature. In this case, T_c = 400 K and T_h = 500 K, so the efficiency is 1 - 400/500 = 0.2. The work done per second is then equal to the heat input per second multiplied by the efficiency, or 10 kJ/s * 0.2 = 2 kJ/s.

An Ideal Frictionless Engine Takes in 10 KJ of Heat