Q. What is the significance of the Carnot efficiency?
A.
It is the maximum possible efficiency of a heat engine
B.
It is the minimum efficiency of any engine
C.
It applies only to refrigeration cycles
D.
It is the efficiency of real engines
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Solution
The Carnot efficiency represents the maximum possible efficiency of a heat engine operating between two temperatures.
Correct Answer:
A
— It is the maximum possible efficiency of a heat engine
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Q. What is the work done by a Carnot engine during one complete cycle if it absorbs Q_H from the hot reservoir?
A.
Q_H - Q_C
B.
Q_C - Q_H
C.
Q_H + Q_C
D.
Q_H * Q_C
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Solution
The work done by a Carnot engine is equal to the heat absorbed from the hot reservoir minus the heat rejected to the cold reservoir, W = Q_H - Q_C.
Correct Answer:
A
— Q_H - Q_C
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Q. Which of the following is a characteristic of an isothermal process?
A.
Temperature remains constant
B.
Pressure remains constant
C.
Volume remains constant
D.
Entropy remains constant
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Solution
In an isothermal process, the temperature of the system remains constant throughout the process.
Correct Answer:
A
— Temperature remains constant
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Q. Which of the following is a property of pure substances?
A.
Pressure
B.
Temperature
C.
Specific volume
D.
All of the above
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Solution
All of the listed options (pressure, temperature, specific volume) are properties of pure substances.
Correct Answer:
D
— All of the above
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Q. Which of the following statements is true regarding heat engines?
A.
They can convert all heat into work
B.
They must operate between two heat reservoirs
C.
They can operate without a working fluid
D.
They are 100% efficient
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Solution
Heat engines must operate between two heat reservoirs, as they require a temperature difference to convert heat into work.
Correct Answer:
B
— They must operate between two heat reservoirs
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Q. Which of the following statements is true regarding heat transfer by convection?
A.
It requires a medium
B.
It occurs in solids only
C.
It is always faster than conduction
D.
It does not involve fluid motion
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Solution
Heat transfer by convection requires a medium, typically a fluid, and involves the bulk movement of that fluid.
Correct Answer:
A
— It requires a medium
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Q. Which of the following statements is true regarding heat transfer?
A.
Heat flows from cold to hot spontaneously
B.
Heat transfer requires a medium
C.
Heat can be transferred by conduction, convection, and radiation
D.
Heat transfer is always efficient
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Solution
Heat can be transferred by conduction, convection, and radiation, which are the three primary modes of heat transfer.
Correct Answer:
C
— Heat can be transferred by conduction, convection, and radiation
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Q. Which property is NOT a characteristic of pure substances?
A.
Defined melting point
B.
Defined boiling point
C.
Variable specific heat
D.
Single chemical composition
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Solution
Pure substances have a defined melting point and boiling point, and they consist of a single chemical composition, but their specific heat can vary with temperature.
Correct Answer:
C
— Variable specific heat
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