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Q. 20

Expert-verified
Found in: Page 595

### Physics for Scientists and Engineers: A Strategic Approach with Modern Physics

Book edition 4th
Author(s) Randall D. Knight
Pages 1240 pages
ISBN 9780133942651

# What are (a) the heat extracted from the cold reservoir and (b) the coefficient of performance for the refrigerator shown in Figure Ex-?

(a)The heat extracted from the cold reservoir,

(b)The coefficient of performance for the refridgerator

See the step by step solution

## Step: 1 Finding the value of workdone: (part a)

Net work done by the gas can be calculated as follows. This is the energy which is required to be served by external electrical power .

Electrical power used up = 119 J - 78 J = 41 J .

105 J is the total heat given out to the environment . This heat will be the sum of heat extracted and electrical energy used.

We can calculate the heat extracted as follows.

## Step: 2 Finding the value of : (part b)

The thermal efficiency is the ratio of the amount of heat extracted from a cold reservoir to the electrical energy required to extract it.. That is,