An engine manufacturer makes the claim that the engine they have developed will, on each cycle take 100 J of heat out of boiling water at 100 °C, do mechanical work of 80J, and exhaust 20 J of heat at 10 °C.

What, if anything, is wrong with this claim?

A) There is nothing wrong with this claim because 100 J = 20 J + 80 J.

B) This engine violates the first law of thermodynamics because 100 J + 20 J ≠ 80 J.

C) An engine would operate by taking in heat at the lower temperature and exhausting heat at a higher temperature.

D) The heat exhausted must always be greater than the work done according to the second law of thermodynamics.

E) The efficiency of this engine is greater than the ideal Carnot cycle efficiency.

Question

Desmond Keller

Physics

27 February, 13:27

An engine manufacturer makes the claim that the engine they have developed will, on each cycle take 100 J of heat out of boiling water at 100 °C, do mechanical work of 80J, and exhaust 20 J of heat at 10 °C.

What, if anything, is wrong with this claim?

A) There is nothing wrong with this claim because 100 J = 20 J + 80 J.

B) This engine violates the first law of thermodynamics because 100 J + 20 J ≠ 80 J.

C) An engine would operate by taking in heat at the lower temperature and exhausting heat at a higher temperature.

D) The heat exhausted must always be greater than the work done according to the second law of thermodynamics.

E) The efficiency of this engine is greater than the ideal Carnot cycle efficiency.

+3

Answers (1)

Know the Answer?

Dereon Figueroa · Answer 1

Heat absorbed, QH = 100 J

Heat exhausted, Qc = 20 J

Mechanical work, W = 80 J

Temperature of hot surface, TH = 100°C = 373 K

Temperature of cold surface, Tc = 10°C = 283 K

According to the carnot's engine

TH / Tc = 373 / 283 = 1.32

And QH / Qc = 100 / 20 = 5

They are not equal to each other, so the engine is not possible.

Option (D)