During each cycle, a heat engine with an efficiency of 25% takes in 800J of energy. How much waste heat energy is expelled in each cycle?
Correct answer: D. 600J
- A. 100J
- B. 200J
- C. 400J
- D. 600J
Explanation
If the efficiency of the engine is 25%, then the energy that is output for useful work is 25% of the input energy, which is 25% of 800 J= 200 J. The remaining 800 J - 200 J = 600 J is expelled as waste heat.
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About First Law of Thermodynamics
The first law relates heat supplied, work done and the change in internal energy through energy conservation. Problems use sign conventions and apply the law to isothermal, adiabatic, isobaric and isochoric processes. Internal energy is a state function, while heat and work depend on the path followed.
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