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den301095 [7]
4 years ago
5

An engine draws energy from a hot reservoir with a temperature of 1250 K and exhausts energy into a cold reservoir with a temper

ature of 378 K. Over the course of one hour, the engine absorbs 1.42 × 10^5 J from the hot reservoir and exhausts 7.5 × 10^4 J into the cold reservoir.
a. What is the power output of this engine?
b. What is the maximum (Carnot) efficiency of a heat engine running between these two reservoirs?
c. What is the actual efficiency of this engine?
Physics
1 answer:
bixtya [17]4 years ago
6 0

Answer:

a. P=18.61\ W

b. \eta_c=0.6976=69.76\%

c. \eta=0.4718=47.18\%

Explanation:

Given:

  • temperature of the hotter reservoir, T_H=1250\ K
  • temperature of the colder reservoir, T_C=378\ K
  • heat absorbed by the engine, Q_H=1.42\times 10^{5}\ J
  • heat rejected to the cold reservoir, Q_L=7.5\times 10^4\ J
  • time duration of the energy transfer, t=1\ hr=3600\ s

<u>Now the work done by the engine:</u>

Using energy conservation,

W=Q_H-Q_L

W=14.2\times 10^4-7.5\times 10^4

W=6.7\times 10^4\ J

a.

<u>Hence the power output:</u>

P=\frac{W}{t}

P=\frac{6.7\times 10^4}{3600}

P=18.61\ W

b.

\eta_c=1-\frac{T_L}{T_H}

\eta_c=1-\frac{378}{1250}

\eta_c=0.6976=69.76\%

c.

now actual efficiency:

\eta=\frac{W}{Q_H}

\eta=\frac{6.7\times 10^4}{1.42\times 10^{5}}

\eta=0.4718=47.18\%

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From the question given above, the following data were obtained:

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Case 2

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What is the efficiency of a device that takes in 400 J of heat and does 120 J
777dan777 [17]

The efficiency of the device is 30 %

Explanation:

The efficiency of a heat engine is given by:

\eta = \frac{W}{Q_{in}}

where

W is the work done by the engine

Q_{in} is the heat in input to the engine

For the device in this problem, we have:

W = 120 J is the work done

Q_{in} = 400 J is the heat in input

Substituting, we find the efficiency:

\eta=\frac{120}{400}=0.30

which corresponds to an efficiency of 30%.

Learn more about work:

brainly.com/question/6763771

brainly.com/question/6443626

#LearnwithBrainly

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