23. The Second Law of Thermodynamics

Heat Engines and the Second Law of Thermodynamics

Multiple Choice
A heat engine exhausts $250 J$ per cycle while doing $200 J$ of work. What is the efficiency of this engine?
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Multiple Choice
Your car's engine can be modeled as a heat engine. How many joules must be extracted from your gas tank to get your $1200 kg$ car to 26 m/s? Assume the thermal efficiency of your car is 16%. Ignore air resistance and other frictional effects on your car.
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Multiple Choice
Which of the following best defines the thermal efficiency of a heat engine?
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Multiple Choice
To increase the maximum efficiency of a heat engine operating between two thermal reservoirs, which of the following should be done according to the second law of thermodynamics?
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Multiple Choice
Why must every heat engine have a cold reservoir?
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Multiple Choice
In each cycle, a heat engine absorbs $1200 J$ from a 400°C hot reservoir, emits $600 J$ to 80°C cold reservoir, while doing $600 J$ of work. Is it physically possible for this engine to exist?
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Multiple Choice
Which of the following best completes the sentence: A heat engine is a device that uses $Q$ to produce useful work?
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Multiple Choice
A heat engine absorbs $500 J$ of heat from a hot reservoir and does $200 J$ of work in one cycle. How much heat is exhausted to the cold reservoir?
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Multiple Choice
In a modern power plant, how is heat energy typically used to generate electricity?
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Multiple Choice
Why is thermal energy produced by a heat engine not generally usable to do work?
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Multiple Choice
Which statement best describes how the $2^{n d}$ law of thermodynamics relates to the operation of heat engines?
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Multiple Choice
Which statement most accurately describes the second law of thermodynamics?
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Multiple Choice
According to the second law of thermodynamics, which of the following actions will increase the maximum possible efficiency of a heat engine operating between two thermal reservoirs?
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Multiple Choice
A heat engine absorbs $500 J$ of heat from a high-temperature reservoir and expels $390 J$ of heat to a low-temperature reservoir in each cycle. What is the approximate efficiency of the heat engine?
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Multiple Choice
In each cycle, a heat engine absorbs $1200 J$ from a 400°C hot reservoir, emits $700 J$ to 80°C cold reservoir, while doing $500 J$ of work. Is it physically possible for this engine to exist?
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