Question

The reservoir temperatures for heat engines A through D are given below. Rank the engines in order of increasing efficiency. Indicate ties where appropriate.

Engine	A	B	C	D
TT hh (K)(K)	400	440	800	1240
TT cc (K)(K)	200	420	600	1020

Rank from largest to smallest. To rank items as equivalent, overlap them._

Answer 1

efficiency is found as

e = 1 - ( T_c / T_h )

so,

for given data, efficiencies are:

Engine A

e = 1 - 200 /400 = 0.5 = 50 %

Engine B

e = 1 - 420 / 440 = 0.045 = 4.5 %

Engine C

e = 1 - 600 / 800 = 0.25 = 25 %

Engine D

e = 1 - 1020 / 1240 = 0.177 = 17.7 %

so,

ranking is

A > C > D > B