An engine manufacturer makes the claim that the engine they have developed will,
ID: 1517864 • Letter: A
Question
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 80 J, and exhaust 20 J of heat at 10°C. What, if anything, is wrong with this claim?
a) The heat exhausted must always be greater than the work done according to the second law of thermodynamics.
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 the higher temperature.
d) The efficiency of this engine is greater than the ideal Carnot cycle efficiency.
e) There is nothing wrong with this claim because 100 J = 20 J + 80 J.
Explanation / Answer
Carnot cycle efficiency = 1- Tc/Th
= 1- ( 10+273.15) / ( 100+273.15) = 0.2412 or 24.12 %
so this can convert only 24.12 heat to work which is = 100* 0.2412 = 24.12 J
so work should be only 24.12 J
but efficiency of this engin =80 / 100 *100 = 80 % so
d) The efficiency of this engine is greater than the ideal Carnot cycle efficiency.