Applications of the Second Law: Thermodynamics for Engineers

Question 1

An ideal refrigerator operates between reservoirs at temperatures T_1 and T_2. The coefficient of performance (COP) of this refrigerator is given by:

Accepted Answer

(Q_1)/(Q_1 - Q_2)

Answer

(Q_2)/(Q_2 - Q_1)

Answer

(Q_1)/W

Answer

(Q_2)/W

Question 2

In a reversible heat engine, the ratio of the work done to the heat absorbed is:

Accepted Answer

Equal to the Carnot efficiency

Answer

Less than the Carnot efficiency

Answer

Equal to zero

Answer

Greater than the Carnot efficiency

Question 3

The Rankine cycle is a model for:

Accepted Answer

Steam power plants

Answer

Internal combustion engines

Answer

Refrigerators

Answer

Air conditioners

Question 4

An air conditioner is an example of a device that:

Accepted Answer

Transfers heat from a cold reservoir to a hot reservoir

Answer

Violates the Second Law of Thermodynamics

Answer

Operates reversibly

Answer

Has a COP less than 1

Question 5

The entropy change of a system during an adiabatic process is:

Accepted Answer

Zero

Answer

Positive

Answer

Negative

Answer

Dependent on the specific heat of the system

Question 6

According to the Second Law of Thermodynamics, which condition is essential for refrigeration systems to function?

Accepted Answer

Refrigeration systems can generate a cold reservoir colder than the surrounding environment.

Answer

No energy input is needed.

Answer

A coefficient of performance exceeding 1 is achievable.

Answer

Refrigeration systems can operate reversibly.

Question 7

The maximum possible efficiency of a heat engine operating between two reservoirs at different temperatures is given by:

Accepted Answer

The difference in temperature between the reservoirs divided by the temperature of the hot reservoir.

Answer

100%

Answer

50%

Answer

The temperature of the hot reservoir minus the temperature of the cold reservoir.

Question 8

The entropy change of a closed system during an irreversible process is:

Accepted Answer

Positive.

Answer

Zero.

Answer

Negative.

Answer

Equal to the entropy change of the surroundings.

Question 9

The Clausius inequality states that the total entropy of a system and its surroundings:

Accepted Answer

Never decreases.

Answer

Always decreases.

Answer

Remains constant.

Answer

Can increase or decrease.

Question 10

A thermodynamic process that can be reversed without changing the entropy of the system or its surroundings is known as a:

Accepted Answer

Reversible process.

Answer

Irreversible process.

Answer

Adiabatic process.

Answer

Isobaric process.

Question 11

At absolute zero, the entropy of a pure substance is:

Accepted Answer

Zero.

Answer

Maximum.

Answer

Minimum.

Answer

Undefined.

Question 12

A refrigerator functions by:

Accepted Answer

Transferring heat from a colder reservoir to a hotter reservoir.

Answer

Converting electrical energy into heat energy.

Answer

Increasing the temperature of a closed system.

Answer

Decreasing the entropy of its surroundings.

Question 13

Which of the following statements about entropy is correct?

Accepted Answer

Entropy measures the level of disorder in a system.

Answer

Entropy decreases in isolated systems.

Answer

Entropy is a conserved quantity.

Answer

Entropy is inversely proportional to temperature.

Question 14

The efficiency of a power plant operating on the Rankine cycle depends on:

Accepted Answer

A combination of the above factors

Answer

The temperature of the heat source

Answer

The temperature of the heat sink

Answer

The pressure ratio of the cycle

Question 15

Which device directly converts heat energy into electrical energy?

Accepted Answer

Thermoelectric generator

Answer

Heat engine

Answer

Refrigerator

Answer

Air conditioner

Question 16

Compare the Otto and Diesel cycles, highlighting the key differences in their compression ratios and fuel types. Analyze how these variations impact their efficiency characteristics.

Accepted Answer

The Otto cycle operates with a lower compression ratio and utilizes gasoline, while the Diesel cycle employs a higher compression ratio and diesel fuel.

Answer

Both Otto and Diesel cycles operate with comparable compression ratios and utilize gasoline as fuel.

Answer

The Otto cycle employs a higher compression ratio and diesel fuel, while the Diesel cycle operates with a lower compression ratio and gasoline.

Answer

Both Otto and Diesel cycles utilize comparable compression ratios and diesel fuel.

Question 17

Which of the following statements accurately describes the Second Law of Thermodynamics?

Accepted Answer

It is impossible to create a heat engine that converts 100% of heat into work.

Answer

Entropy decreases in isolated systems.

Answer

Heat flows spontaneously from cold to hot objects.

Question 18

A refrigerator primarily functions by:

Accepted Answer

Transferring heat from a cold reservoir to a hot reservoir.

Answer

Increasing the entropy of the cold reservoir.

Answer

Converting heat directly into mechanical energy.

Question 19

Which of the following heat engine types operates with the highest theoretical efficiency?

Accepted Answer

Carnot engine

Answer

Stirling engine

Answer

Diesel engine

Answer

Otto engine

Question 20

The change in entropy of a closed system undergoing a reversible process is:

Accepted Answer

Zero

Answer

Negative

Answer

Positive

Question 21

Which statement is NOT a consequence of the Second Law of Thermodynamics?

Accepted Answer

Friction always decreases the entropy of a system.

Answer

The universe tends towards increasing disorder.

Answer

Heat engines cannot achieve 100% efficiency.

Question 22

A power plant primarily operates by:

Accepted Answer

Converting thermal energy into mechanical energy and then into electrical energy.

Answer

Transferring heat from a cold reservoir to a hot reservoir.

Answer

Increasing the entropy of the system.

Question 23

The Clausius statement of the Second Law of Thermodynamics asserts that:

Accepted Answer

Heat cannot spontaneously flow from a colder to a hotter body.

Answer

The efficiency of heat engines is inversely proportional to the temperature difference.

Answer

Entropy increases in closed systems.

Question 24

An important application of the Second Law of Thermodynamics in refrigeration is:

Accepted Answer

Designing systems to extract heat from food and beverages.

Answer

Propelling vehicles

Answer

Generating electricity for power plants