Physics

Problem

An irreversible heat engine (E) and an ideal refrigerator (R) operate between the same hot reservoir at

500\,\text{K}

and cold reservoir at

300\,\text{K}

. In one cycle: • Engine E absorbs

400\,\text{J}

from the hot reservoir and rejects

250\,\text{J}

to the cold reservoir. • Refrigerator R extracts

120\,\text{J}

from the cold reservoir and delivers

200\,\text{J}

to the hot reservoir. For the combined device (E + R) running one cycle, the net change in entropy of the universe is a)

0\,\text{J\,K}^{-1}

+0.50\,\text{J\,K}^{-1}

+0.033\,\text{J\,K}^{-1}

-0.033\,\text{J\,K}^{-1}