Help session. mast Copy of PHYC 150 3le Chapter 11 Problem 11.59 e pre Problem 1

Question

Help session. mast Copy of PHYC 150 3le Chapter 11 Problem 11.59 e pre Problem 11.59 Part A The coefficient of performance of a refrigerator is 3.9. The compressor uses 10 J of energy per cycle. How much heat energy is exhausted per cycle? Express your answer using two significant figures. 490 J Submit My Answers Give Up Correct Part B If the hot-reservor temperature is 28 ° C, what is the lowest possible temperature in( reservoir? Express your answer using two significant figures. 34 36 .42 1.53 1.57 My Answers Give Up ncorrect: Try Again; 6 attempts remaining 11.59 11.63 m 11.67 1.1: Energy rst Law of Engines Introduced 16

Explanation / Answer

Ans:-

a)
The fridge is heat a pump used for cooling. For such operation coefficient of performance is defined as ratio of heat extracted from cold reservoir to the work done on the pump:
COP = Qc/W
=>
Qc = W COP = 10J * 3.9 = 39J

Conservation of energy requires that the total energy absorbed by work and heat from cold reservoir is exhausted to the hot reservoir, i.e.
Qh = W + Qc = 10J + 39J = 49J


b)
COP Tc/(Th - Tc)

COP*(Th - Tc) Tc  
Tc Th*COP/(COP + 1)

Tc (28 + 273)K * 3.9/(3.9 + 1)

Tc 240K = -33°C

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