 Solution

ID: past-exam-of-the-physics-b-course-of-the-university-of-cambridge/2014/paper-2/section-c/c10/solution

A heat engine operates cyclically, absorbing heat

Q_{h}

from a hotter source, rejecting heat

Q_{c}

to a colder sink and delivering net work

W = Q_{h} - Q_{c}

. Its efficiency is

η = W / Q_{h}

. The working substance returns to its original state; the reservoirs and surroundings need not.

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