Physics 11th Chap 8 : Topic 13 - Maryam Publications

Physics Chapter 8 : Topic 13

Heat Engines

1 / 30

The basic working principle of a heat engine is to:

A) Convert all heat energy into internal energy

B) Convert mechanical work into heat only

C) Destroy unwanted heat energy

D) Convert heat energy into mechanical work

2 / 30

A heat engine operates between:

A) A vacuum and a heat source

B) A hot reservoir and a cold reservoir

C) Two bodies having the same temperature

D) Two cold reservoirs only

3 / 30

The main energy input to a heat engine is:

A) Heat energy from a high-temperature source

B) Electrical energy

C) Chemical energy only

D) Mechanical energy

4 / 30

A heat engine converts heat into work by:

A) Stopping molecular motion

B) Transferring all heat to the cold reservoir

C) Increasing internal energy permanently

D) Using part of the absorbed heat to perform mechanical work

5 / 30

In a heat engine, the heat absorbed from the hot reservoir is represented by:

A) $\mathbf{Q}_{\mathbf{H}}$

B) $\mathbf{W}$

C) $\mathbf{Q}_{\mathbf{C}}$

D) $\mathbf{\mathrm{\Delta}U}$

6 / 30

The useful output of a heat engine is:

A) Internal energy

B) Mechanical work

C) Rejected heat

D) Temperature increase

7 / 30

The energy balance of a heat engine is:

A) $\mathbf{Q}_{\mathbf{C}}\mathbf{=}\mathbf{Q}_{\mathbf{H}}\mathbf{+ W}$

B) $\mathbf{Q}_{\mathbf{H}}\mathbf{=}\mathbf{Q}_{\mathbf{C}}\mathbf{- W}$

C) $\mathbf{W =}\mathbf{Q}_{\mathbf{H}}\mathbf{-}\mathbf{Q}_{\mathbf{C}}$

D) $\mathbf{W =}\mathbf{Q}_{\mathbf{H}}\mathbf{+}\mathbf{Q}_{\mathbf{C}}$

8 / 30

A heat engine cannot convert all absorbed heat into work because:

A) Temperature has no role.

B) Work cannot be produced.

C) Some heat must be rejected to a lower-temperature reservoir.

D) Heat has no energy.

9 / 30

The component of a heat engine that receives heat is called:

A) Cold reservoir

B) Heat sink

C) Working substance

D) Insulator

10 / 30

In a heat engine, the working substance:

A) Remains unchanged throughout operation

B) Does not exchange energy

C) Always loses heat only

D) Undergoes a cyclic process

11 / 30

The purpose of the cold reservoir in a heat engine is to:

A) Increase engine temperature

B) Supply heat to the engine

C) Absorb rejected heat

D) Produce mechanical energy

12 / 30

Which sequence correctly describes heat engine operation?

A) Cold reservoir $\overset{\mathbf{\ \ \ \ \ \ \ \ \ \ \ \ }}{\rightarrow}$ engine $\overset{\mathbf{\ \ \ \ \ \ \ \ \ \ \ \ }}{\rightarrow}$ hot reservoir

B) Work $\overset{\mathbf{\ \ \ \ \ \ \ \ \ \ \ \ }}{\rightarrow}$ engine $\overset{\mathbf{\ \ \ \ \ \ \ \ \ \ \ \ }}{\rightarrow}$ heat source

C) Hot reservoir $\overset{\mathbf{\ \ \ \ \ \ \ \ \ \ \ \ }}{\rightarrow}$ engine $\overset{\mathbf{\ \ \ \ \ \ \ \ \ \ \ \ }}{\rightarrow}$ cold reservoir

D) Engine $\overset{\mathbf{\ \ \ \ \ \ \ \ \ \ \ \ }}{\rightarrow}$ hot reservoir $\overset{\mathbf{\ \ \ \ \ \ \ \ \ \ \ \ }}{\rightarrow}$ cold reservoir

13 / 30

The efficiency of a heat engine is defined as:

A) Heat input / work output

B) Heat rejected / heat absorbed

C) Work output / heat rejected

D) Work output / heat input

14 / 30

The efficiency of a heat engine can never be:

A) $\mathbf{20\%}$

B) $\mathbf{100\%}$

C) $\mathbf{90\%}$

D) $\mathbf{50\%}$

15 / 30

If a heat engine absorbs $\mathbf{1000\ J}$ heat and rejects $\mathbf{600\ J}$, the work output is:

A) $\mathbf{600\ J}$

B) $\mathbf{400\ J}$

C) $\mathbf{1000\ J}$

D) $\mathbf{1600\ J}$

16 / 30

A heat engine with higher efficiency:

A) Produces more work from the same heat input

B) Produces no work

C) Rejects all absorbed heat

D) Requires no heat source

17 / 30

The operation of a heat engine depends on:

A) Temperature difference between reservoirs

B) Zero pressure difference only

C) Absence of heat transfer

D) Equal temperature reservoirs

18 / 30

If the hot reservoir and cold reservoir have the same temperature, a heat engine:

A) Converts all heat into energy

B) Works at maximum efficiency

C) Produces unlimited work

D) Cannot produce continuous work

19 / 30

A car engine is an example of:

A) Heat engine

B) Refrigerator

C) Heat sink

D) Thermometer

20 / 30

A steam engine works by:

A) Preventing expansion of steam

B) Removing all internal energy

C) Converting heat energy of steam into mechanical work

D) Converting work into heat only

21 / 30

During expansion in a heat engine, the working substance:

A) Receives mechanical work only

B) Does work on surroundings

C) Stops moving

D) Loses all energy

22 / 30

Which statement about a heat engine is correct?

A) It does not require temperature difference.

B) It transfers energy from a hot source and converts part of it into work.

C) It violates conservation of energy.

D) It converts all heat into work.

23 / 30

The rejected heat in a heat engine:

A) becomes mechanical work

B) disappears from the system

C) is completely wasted energy

D) is transferred to the cold reservoir

24 / 30

Which change can increase the maximum possible efficiency of a heat engine?

A) Increasing the temperature of hot reservoir

B) Removing the cold reservoir

C) Making both reservoirs equal in temperature

D) Decreasing temperature difference

25 / 30

A heat engine operating in a cycle has:

A) No work output

B) No net change in internal energy of working substance

C) Continuously increasing internal energy

D) No heat transfer

26 / 30

Which device works opposite to a heat engine?

A) Steam engine

B) Turbine

C) Refrigerator

D) Petrol engine

27 / 30

A heat engine requires a low-temperature sink because:

A) Pressure must remain zero

B) Work cannot be produced

C) Some heat must leave the working substance

D) Heat must be completely destroyed

28 / 30

The working substance in a heat engine may be:

A) Steam or gas

B) Vacuum only

C) Only solid metal

D) Only liquid water

29 / 30

The efficiency of a heat engine is always less than $\mathbf{1}$ because:

A) Energy is destroyed

B) Work output is greater than heat input

C) Heat input is zero

D) Some heat is rejected to the sink

30 / 30

The fundamental principle behind the working of a heat engine is:

A) Heat can be partially converted into work when flowing from hot to cold.

B) Energy is created during expansion.

C) Heat naturally flows from cold to hot.

D) Work cannot change into heat.

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