First Law of Thermodynamics: Energy Conservation in Thermodynamic Systems

Question 1

The first law of thermodynamics is also known as:

Accepted Answer

Conservation of Energy

Answer

Conservation of Mass

Answer

Heat Transfer Law

Answer

Work-Energy Theorem

Question 2

In an adiabatic process, which of the following remains constant?

Accepted Answer

Entropy

Answer

Volume

Answer

Pressure

Answer

Temperature

Question 3

The change in internal energy of a system is equal to:

Accepted Answer

Heat added to the system minus work done by the system

Answer

Heat added to the system plus work done by the system

Answer

Heat removed from the system plus work done by the system

Answer

Heat removed from the system minus work done by the system

Question 4

Which of the following is a unit of energy?

Accepted Answer

Joule

Answer

Newton

Answer

Pascal

Answer

Watt

Question 5

In an open system, what is allowed to cross the system boundary?

Accepted Answer

Energy and mass

Answer

Mass only

Answer

Energy only

Answer

Neither energy nor mass

Question 6

The efficiency of a heat engine is:

Accepted Answer

Work output divided by heat input

Answer

Heat input divided by work output

Answer

Work input minus heat output

Answer

Heat output minus work input

Question 7

Which of the following processes is irreversible?

Accepted Answer

Free expansion

Answer

Isothermal expansion

Answer

Adiabatic compression

Answer

Isochoric heating

Question 8

The entropy of a system is a measure of:

Accepted Answer

Disorder

Answer

Order

Answer

Energy

Answer

Temperature

Question 9

The First Law of Thermodynamics is based on the fundamental principle of:

Accepted Answer

Energy conservation

Answer

Energy creation and destruction

Answer

Energy dissipation

Answer

Energy conversion without loss

Question 10

Which of the following is NOT a recognized mode of energy transfer in thermodynamics?

Accepted Answer

Mass

Answer

Heat

Answer

Work

Answer

Radiation

Question 11

The work done by a system is considered

Accepted Answer

Positive when the system's volume increases

Answer

Positive when heat is added to the system

Answer

Negative when heat is removed from the system

Answer

Negative when the system's pressure decreases

Question 12

The change in a system's internal energy is mathematically expressed as:

Accepted Answer

Heat added minus work done

Answer

Work done minus heat removed

Answer

Heat capacity multiplied by temperature change

Answer

Mass multiplied by specific heat multiplied by temperature change

Question 13

An open system in thermodynamics is one that:

Accepted Answer

Can freely exchange both heat and mass with its surroundings

Answer

Can exchange only heat

Answer

Can exchange only mass

Answer

Can exchange neither heat nor mass

Question 14

Which of the following processes exemplifies an adiabatic process?

Accepted Answer

Expansion of a gas in a sealed, insulated container

Answer

Fuel combustion in an engine cylinder

Answer

Cooling of a hot object exposed to air

Answer

Transfer of heat between two objects at different temperatures

Question 15

The efficiency of a heat engine, as defined in thermodynamics, is the ratio of:

Accepted Answer

Work done by the engine to heat added to the engine

Answer

Heat added to the engine to work done by the engine

Answer

Heat rejected by the engine to heat added to the engine

Answer

Heat rejected by the engine to work done by the engine

Question 16

The Carnot cycle is a hypothetical heat engine cycle that:

Accepted Answer

Achieves the maximum possible efficiency

Answer

Produces zero heat rejection

Answer

Is impractical to implement

Answer

Exclusively consists of isothermal processes

Question 17

Which limitation of the First Law of Thermodynamics prevents it from predicting the direction of spontaneous processes?

Accepted Answer

Considers only energy changes, not entropy

Answer

Assumes reversible processes

Answer

Applies only to equilibrium systems

Question 18

According to the First Law of Thermodynamics, which of the following holds true for a closed system?

Accepted Answer

The total amount of energy remains constant.

Answer

Energy can be created or destroyed.

Answer

Heat is converted into work without any losses.

Answer

Entropy always decreases.

Question 19

Which of the following is an example of an open system in thermodynamics?

Accepted Answer

A car engine exchanging heat with its surroundings

Answer

A sealed container with a gas inside

Answer

A closed bottle of water

Answer

A refrigerator operating at a constant temperature

Question 20

The efficiency of a heat engine is defined as:

Accepted Answer

The ratio of work output to heat input

Answer

The ratio of heat input to work output

Answer

The difference between heat input and work output

Answer

The product of heat input and work output

Question 21

In a polytropic process, the relationship between pressure and volume is described by:

Accepted Answer

PV^n = constant

Answer

PV = constant

Answer

P/V = constant

Answer

V/P = constant

Question 22

During a reversible process, the change in entropy of the system is:

Accepted Answer

Equal to zero

Answer

Greater than zero

Answer

Less than zero

Answer

Indeterminate

Question 23

According to the First Law of Thermodynamics, which statement is true regarding energy?

Accepted Answer

Energy can be transferred or transformed, but not created or destroyed.

Answer

Energy can be created or destroyed.

Answer

Energy is always conserved within a closed system.

Answer

Energy can only be transferred in the form of heat.

Question 24

In a closed system, energy transfer can take place in which forms?

Accepted Answer

Heat and work only

Answer

Heat and mass only

Answer

Work and mass only

Answer

Heat, work, and mass

Question 25

Which of the following is NOT a valid application of the First Law of Thermodynamics?

Accepted Answer

Determining the change in gravitational potential energy

Answer

Analyzing heat engines

Answer

Calculating the work done by a compressor

Answer

Modeling the performance of a refrigeration system

Question 26

Consider a closed system. If heat is added to the system without performing any work on it, what will happen to its internal energy?

Accepted Answer

Increase

Answer

Decrease

Answer

Remain constant

Answer

Become zero

Question 27

Which statement correctly describes open systems?

Accepted Answer

Mass and energy can both enter and leave the system.

Answer

Mass cannot enter or leave the system.

Answer

Energy can only enter or leave the system as heat.

Answer

Open systems are always at equilibrium.

Question 28

Which unit is used to measure the specific heat of a substance?

Accepted Answer

Joules per kilogram-degree Celsius

Answer

Calories per gram-degree Fahrenheit

Answer

Watts per meter-second

Answer

Newtons per square meter

Question 29

An adiabatic system is characterized by:

Accepted Answer

No heat transfer between the system and its surroundings

Answer

The system is always at equilibrium

Answer

The system has a constant volume

Answer

The system has a constant pressure

Question 30

According to the First Law of Thermodynamics, what is a requirement for the operation of a heat pump?

Accepted Answer

Having the total energy entering the heat pump equal the total energy leaving the heat pump

Answer

Transferring more heat out of the cold reservoir than into the warm reservoir

Answer

Using more energy than the amount of heat transferred to the warm reservoir

Answer

Transferring heat from the cold reservoir to the warm reservoir without any energy input

Question 31

According to the First Law of Thermodynamics, energy in an isolated system:

Accepted Answer

Remains constant.

Answer

Can be created or destroyed.

Answer

Is transferred in the form of heat and work.

Answer

Increases over time.

Question 32

In a closed system where heat is added and no work is done, the internal energy:

Accepted Answer

Increases.

Answer

Decreases.

Answer

Remains constant.

Answer

Becomes zero.

Question 33

Which thermodynamic property measures the randomness or disorder of a system?

Accepted Answer

Entropy

Answer

Internal energy

Answer

Enthalpy

Answer

Specific heat capacity

Question 34

Which factor does NOT influence the maximum efficiency of a Carnot engine?

Accepted Answer

Size of the engine

Answer

Temperature of the heat source

Answer

Temperature of the heat sink

Answer

Working fluid used

Question 35

According to the First Law of Thermodynamics, what happens to the total amount of energy in an isolated system?

Accepted Answer

It remains constant.

Answer

It can be created or destroyed.

Answer

It increases gradually.

Answer

It decreases rapidly.

Question 36

In a closed system, which of the following energy transfers can occur?

Accepted Answer

Heat and work transfer

Answer

Heat transfer only

Answer

Work transfer only

Answer

Mass transfer only

Question 37

Consider a system where the internal energy decreases and external work is done by the system. What can be concluded about the heat transfer?

Accepted Answer

Heat is transferred out of the system.

Answer

Heat is transferred into the system.

Answer

Heat is not transferred.

Answer

The direction of heat transfer cannot be determined.

Question 38

In an open system, the First Law of Thermodynamics takes into account:

Accepted Answer

Energy transfer due to mass flow, heat, and work transfer

Answer

Energy transfer due to mass flow only

Answer

Energy transfer due to heat and work transfer only

Answer

Energy transfer due to internal energy change only

Question 39

In a steam turbine power plant, which process involves heat rejection?

Accepted Answer

Condensation

Answer

Combustion

Answer

Expansion

Answer

Compression

Question 40

In a refrigeration system, the evaporator absorbs heat from:

Accepted Answer

The refrigerated space

Answer

The condenser

Answer

The compressor

Answer

The expansion valve

Question 41

The thermal efficiency of a heat engine is defined as the ratio of:

Accepted Answer

Work output to heat input

Answer

Heat input to work output

Answer

Internal energy change to heat input

Answer

Heat rejected to heat input

Question 42

Which of the following is NOT a form of energy transfer in thermodynamics?

Accepted Answer

Mass

Answer

Heat

Answer

Work

Answer

Radiation

Question 43

In a closed thermodynamic system, energy can be transferred but not:

Accepted Answer

Created or destroyed

Answer

Exchanged

Answer

Converted from one form to another

Answer

Released

Question 44

An open thermodynamic system exchanges both energy and:

Accepted Answer

Mass

Answer

Heat

Answer

Work

Answer

Radiation

Question 45

During an adiabatic process, the change in internal energy of a system is:

Accepted Answer

Zero

Answer

Equal to the heat transferred

Answer

Equal to the work done

Answer

Equal to the sum of heat transferred and work done

Question 46

The efficiency of a heat engine is defined as the:

Accepted Answer

Ratio of work output to heat input

Answer

Ratio of heat input to work output

Answer

Ratio of heat absorbed to heat rejected

Answer

Ratio of work done to heat transferred

Question 47

Which of the following factors affects the efficiency of a Carnot cycle thermodynamic engine?

Accepted Answer

Both temperature of the heat source and temperature of the heat sink

Answer

Temperature of the heat source

Answer

Temperature of the heat sink

Answer

Neither temperature of the heat source nor temperature of the heat sink

Question 48

In essence, what does the First Law of Thermodynamics state?

Accepted Answer

Energy cannot be produced or destroyed, just transferred or changed in form.

Answer

Heat engines can reach 100% efficiency.

Answer

Heat inevitably travels from warmer to cooler objects.

Question 49

In an open system:

Accepted Answer

Mass can traverse the system boundary.

Answer

Volume remains constant.

Answer

There's no energy exchange across the system boundary.

Question 50

A heat engine is a device that converts:

Accepted Answer

Thermal energy into mechanical work.

Answer

Mechanical work directly into thermal energy.

Answer

Chemical energy directly into thermal energy.

Answer

Electrical energy into thermal energy.

Question 51

Heat engine efficiency is defined as:

Accepted Answer

Ratio of net work output to heat input.

Answer

Change in temperature of the working fluid.

Answer

Ratio of heat output to net work input.

Question 52

Which process is reversible?

Accepted Answer

A process that can be reversed without altering the system or surroundings.

Answer

A process that cannot be reversed.

Answer

A process that can be reversed with some change in the system or surroundings.

Question 53

Entropy measures:

Accepted Answer

The disorder or randomness of a system.

Answer

Temperature of a system.

Answer

Energy of a system.

Question 54

According to the Second Law of Thermodynamics:

Accepted Answer

In an isolated system, entropy always increases.

Answer

In an isolated system, entropy stays constant.

Answer

In an isolated system, entropy always decreases.