Question 1

One important feature of the Carnot cycle is that it

Accepted Answer

A)   maximizes the entropy of a heat engine operating between two temperatures.
B)   specifies the operating temperatures of any heat engine.
C)   converts all of the heat flowing into an engine to work.
D)   predicts the maximum efficiency of a heat engine operating between two temperatures.

Question 2

The actual source of wind energy is

Accepted Answer

A)   solar energy
B)   the daily rotation of the Earth on its axis
C)   the tides
D)   the lunar cycleFill in the Blank Questions

Question 3

An amount of water forms a single hexagonally symmetric snowflake. Elsewhere the same amount of water is a droplet of liquid water. Which state has higher entropy?

Accepted Answer

A)   Their entropy levels are the same, since they are actually the same amount of H2O, just different phases.
B)   The droplet of liquid water, since it is more unruly and can adopt almost any shape.
C)   The solid water, since it has a tight restriction to hexagonal symmetry.

Question 4

It is an advantage for an automobile engine to run at a high temperature because

Accepted Answer

A)   its efficiency is higher, since the temperature difference is what dictates efficiency.
B)   gasoline only ignites under high temperature conditions.
C)   a high operating temperature cools off the fuel before ignition.
D)   it allows the use of lighter engine components made from aluminum.

Question 5

Entropy and temperature measure different properties of a sample of a substance, because temperature gauges average kinetic energy of molecules or atoms, but

Accepted Answer

A)   entropy is the inverse of temperature, due to conservation of momentum.
B)   low entropy substances cannot have a temperature.
C)   entropy of an isolated system cannot decrease.
D)   entropy measures disorderliness or unruliness.

Question 6

Energy added to a cyclical heat engine

Accepted Answer

A)   is completely converted to external work.
B)   is converted to work and to waste heat.
C)   is used to generate work that is greater than the added energy.
D)   is converted to increased internal energy in the engine plus external work.

Question 7

The efficiency of an engine can be defined as the

Accepted Answer

A)   ratio of work done to energy input.
B)   total amount of work performed.
C)   ratio of work done to energy exhausted.
D)   ratio of heat exhausted to heat intake.

Question 8

A heat engine takes in 500 J of energy from the hot reservoir in one cycle while performing 100 J of work. The amount of heat transferred to the cold reservoir in the same time is

Accepted Answer

A)   500 J.
B)   400 J.
C)   300 J.
D)   200 J.
E)   zero.

Question 9

Some power plants extract energy from the warm ocean currents. A major disadvantage to these power plants is that

Accepted Answer

A)   the efficiency is quite low.
B)   there is no low temperature reservoir.
C)   the amount of heat released to the environment is unacceptable.
D)   the cost of warm ocean water is quite high.

Question 10

A heat engine that would take in 1000 J of heat from a reservoir at 500 K and exhaust 500 J to a reservoir at 300 K, converting the other 500 J of heat to work, is

Accepted Answer

A)   thermodynamically possible.
B)   possible only for a Carnot cycle.
C)   not thermodynamically possible.

Question 11

When one kilogram of ice at 0$\degree$C is converted to the same amount of water at 0$\degree$C by adding heat, the change in entropy is _______________ (positive, negative, zero).

Accepted Answer

The answer of When one kilogram of ice at 0$\degree$C...

Question 12

In an ideal reversible process such as a Carnot cycle the entropy of the universe ___________________ (increases, decreases, is unchanged).

Accepted Answer

The answer of In an ideal reversible process such as...

Question 13

An engine that decreases the total entropy in the universe is

Accepted Answer

A)   a refrigerator.
B)   a Carnot engine.
C)   a heat pump.
D)   impossible.

Question 14

The efficiency of a Carnot engine would be increased if

Accepted Answer

A)   the high temperature were lowered by 100 °\degree° C.
B)   the low temperature were raised by 100 °\degree° C.
C)   the high and low temperatures were both raised by 100 °\degree° C.
D)   the high and low temperatures were both lowered by 100 °\degree° C.

Question 15

If, for an ideal heat engine, QH , QC, and W are, respectively, the heat absorbed, the heat exhausted, and the work done per cycle, which of these is true?

Accepted Answer

A)   QH cannot be more than W.
B)   QC cannot be more than QH.
C)   W cannot be more than QC.
D)   QH cannot be more than QC.

Question 16

Entropy is

Accepted Answer

A)   another term for heat.
B)   a quantity that is conserved in any thermal process.
C)   a quantity that increases as the disorder of a system increases.
D)   something that never locally decreases in any process.

Question 17

If a Carnot heat engine is run in reverse, it becomes

Accepted Answer

A)   a heat engine with the smallest possible efficiency.
B)   an engine that has a negative efficiency.
C)   a refrigerator.
D)   nothing. It can't be run in reverse because to do so would violate the second law of thermodynamics.

Question 18

A reversible engine is one that

Accepted Answer

A)   does no net work.
B)   causes no increase in net entropy.
C)   generates no net heat.
D)   acts as a refrigerator.

Question 19

The overall direction of change in the universe is toward

Accepted Answer

A)   a state of increased mass in the universe.
B)   increased energy content of the universe.
C)   a state of increased organization.
D)   a state of greater disorder.

Question 20

It is impossible to construct an engine that is more than 100% efficient. The physical law covering this case is

Accepted Answer

A)   the zeroth law of thermodynamics.
B)   the first law of thermodynamics.
C)   Clausius's statement of the second law of thermodynamics.
D)   Kelvin's statement of the second law of thermodynamics.
E)   the third law of thermodynamics.

Exam 11: Heat Engines and the Second Law of Thermodynamics

A heat engine that would take in 1000 J of heat from a reservoir at 500 K and exhaust 500 J to a reservoir at 300 K, converting the other 500 J of heat to work, is

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The efficiency of an engine can be defined as the

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The efficiency of a Carnot engine would be increased if

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It is impossible to construct an engine that is more than 100% efficient. The physical law covering this case is

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A heat engine takes in 500 J of energy from the hot reservoir in one cycle while performing 100 J of work. The amount of heat transferred to the cold reservoir in the same time is

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If a Carnot heat engine is run in reverse, it becomes

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The actual source of wind energy is

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An amount of water forms a single hexagonally symmetric snowflake. Elsewhere the same amount of water is a droplet of liquid water. Which state has higher entropy?

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Entropy is

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When one kilogram of ice at 0 °\degree° C is converted to the same amount of water at 0 °\degree° C by adding heat, the change in entropy is _______________ (positive, negative, zero).

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An engine that decreases the total entropy in the universe is

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The overall direction of change in the universe is toward

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A reversible engine is one that

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Some power plants extract energy from the warm ocean currents. A major disadvantage to these power plants is that

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One important feature of the Carnot cycle is that it

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If, for an ideal heat engine, QH , QC, and W are, respectively, the heat absorbed, the heat exhausted, and the work done per cycle, which of these is true?

Correct AnswerverifiedShow Answer

In an ideal reversible process such as a Carnot cycle the entropy of the universe ___________________ (increases, decreases, is unchanged).

Correct AnswerverifiedShow Answer

Entropy and temperature measure different properties of a sample of a substance, because temperature gauges average kinetic energy of molecules or atoms, but

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It is an advantage for an automobile engine to run at a high temperature because

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Energy added to a cyclical heat engine

Correct AnswerverifiedShow Answer

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When one kilogram of ice at 0 $\degree$ C is converted to the same amount of water at 0 $\degree$ C by adding heat, the change in entropy is _______________ (positive, negative, zero).

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If, for an ideal heat engine, Q_H , Q_C, and W are, respectively, the heat absorbed, the heat exhausted, and the work done per cycle, which of these is true?

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