A composite device consists of two parts working in tandem: • Part A is a…

PHYSICS · Multi-part · CBSE · Physics · Thermodynamics · Thermodynamics

Problem

A composite device consists of two parts working in tandem: • Part A is a hypothetical heat engine that, in each cycle, absorbs

1000\,\text{J}

of heat from a reservoir at

T_H = 600\,\text{K}

and delivers an equal amount of work

W = 1000\,\text{J}

with no heat rejection. • Part B is a refrigerator that uses the entire work output of Part A to transfer

300\,\text{J}

of heat per cycle from a cold reservoir at

T_C = 300\,\text{K}

to the same hot reservoir at

600\,\text{K}

. Analyse the overall effect of the composite device. (i) For one complete cycle, calculate the change in entropy of (a) the hot reservoir, (b) the cold reservoir, and (c) the universe. (ii) Show that the total entropy change of the universe obtained in part (i) is negative. (iii) From your result, explain why the combination of Part A and Part B cannot be realised in practice.

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