Multiple Choice Questions Based on Carnot Engine, Cycle and Theorem Useful For University Exams, IIT, NEET, M. Sc. Entrance and PGT

 

1.The device which convert heat into mechanical work is

    (a) Motor                                                           

    (b) Generator

    (c) Energy Convertor                                      

    (d) Heat Engine

Answer: d

2. Carnot cycle has maximum efficiency for

(a) reversible engine                                                 

(b) irreversible engine

(c) new engine                                                           

(d) petrol engine

Answer : a

3. Carnot cycle efficiency depends upon

(a) properties of the medium/substance used         

(b) condition of engine

(c) working condition                           

(d) temperature range of operation

Answer : d

4. In a Carnot cycle the temperature of the working substance at the end of the cycle is

        (a) Less than that at the beginning

       (b) More than that at the beginning

        (c) Equal to that at the beginning

        (d) Zero

Answer: c

5. Which is most effective for increase of efficiency of Carnot engine

(a)  Increase of temperature of source by 50℃

(b)  decrease of temperature of sink by 50℃

(c)   increase of temperature of source by 25℃ and decrease of temperature of sink by 25℃

(d)  all above are equally effective

Answer: b

6. An engine operates between temperatures of 900°K and T₂ and another engine between T₂ and 400°K For both to do equal work, value of T₂ will be

     (a) 650°K                                                                             

     (b) 600°K

(c) 625°K                                                                              

(d) 700°K

Answer : a

7. Carnot cycle efficiency is maximum when

(a) initial temperature is 0°K                     

(b) final temperature is 0°K

(c) difference between initial and final temperature is 0°K

(d) final temperature is 0°C  

Answer : b

8. If a system after undergoing a series of processes, returns to the initial state then

(a) process is thermodynamically in equilibrium  

(b) process is executed in closed system cycle

(c) its entropy will change due to irreversibility    

(d) sum of heat and work transfer will be zero

Answer : d

9. An actual engine is to be designed having same efficiency as the Carnot cycle. Such a proposition is

(a) feasible                           

(b) impossible

(c) possible                           

(d) possible, but with lot of sophistications

Answer : d

10. In a Carnot cycle, heat is transferred at

(a) constant pressure                               

(b) constant volume

(c) constant temperature                        

(d) constant enthaply

Answer : c

11. A manufacturer claims to have a heat engine capable of developing 20 h.p. by receiving heat input of 400 kcal/mt and working between the temperature limits of 227° C and 27° C. His claim is

(a) justified                                                        

(b) not possible

(c) may be possible with lot of sophistications 

(d) cost will be very high

Answer : b

12. The efficiency of a Carnot engine depends on

(a) working substance                                       

(b) design of engine

(c) size of engine                                                

(d) type of fuel fired

(e) temperatures of source and sink.

Answer : e

13. The efficiency of Carnot cycle is maximum for

(a) gas engine                                           

(b) well lubricated engine

(c) petrol engine                                                

(d) steam engine

(e) reversible engine.

Answer : e

14. Carnot cycle is

(a) a reversible cycle                               

(b) an irreversible cycle

(c) a semi-reversible cycle                                 

(d) a quasi static cycle                     

Answer : a

15. Heat is transferred to a heat engine from a furnace at a rate of 80 MW if the rate of waste heat rejection to a nearby river is 50 MW determine the net power output for this heat engine.

(a) 30MW                

(b) 40MW                

(c) 50MW                    

(d) 60MW

Answer: a

Hint: Net power output =80-50=30MW

16. Heat is transferred to a heat engine from a furnace at a rate of 80 MW if the rate of waste heat rejection to a nearby river is 50 MW. Determine the efficiency for this heat engine. 

(a) 47.5%                

(b) 27.5%               

(c) 37.5%                 

(d)none of above

Answer: c

Hint: Efficiency =output/input 

Efficiency =30/80=.375

17. A reversible engine and an irreversible engine are working between the same temperature. The efficiency of

        (a) both is same                                  

        (b) reversible is greater          

        (c) irreversible is greater                  

        (d) each is 1

Answer: b

18. Absolute scale of temperature was given by

        (a) Carnot                  

        (b) Otto              

        (c) Kelvin               

        (d) Dewar

Answer: c

19. Working substance in Carnot engine is

(a) Helium                  

(b) Hydrogen                

(c) Argon        

(d) Perfect Gas

Answer: d

20. In a Carnot cycle , third step is

(a) Isothermal Compression                               

(b) Adiabatic Compression

(c) Isothermal Expansion                                    

(d) Adiabatic Expansion

Answer: a

21.How are the efficiencies of any heat engine (η) and reversible heat engine (η_R) compared, when both are operating between same heat source and same heat sink?

        (a) η = η_R                                                                   

        (b) η > η_R

        (c) η < η_R                                                                    

        (d) cannot say

Answer: c

 

 

 

Second Law of Thermodynamics (Direction of flow of heat) With MCQS Useful For Different University Exams, IIT, NEET, M.Sc. Entrance, PGT

Kelvin Statement-

It is impossible to get a continuous supply of work from a body by colling it to a temperature lower than that of its surrounding.

Planks Statement-

It is impossible to construct an engine which work in a complete cycle will produce no effect other than the raising of a weight and cooling of a reservoir.

Kelvin-Plank Statement-

It is impossible to construct an engine which operating in a cycle has the sole effect of extracting heat from a reservoir and performing an equivalent amount of work.

Clausius Statement-

It is impossible for a self-acting machine working in a cyclic process unaided by external agency to transfer heat from a body at a lower temperature to a body at a higher temperature.

1. Kelvin Planck’s law deals with

(a) conservation of heat                                          

(b) conservation of work

(c) conversion of heat into work                            

(d) conversion fo work into heat

Answer : c

2. According to Clausius statement of second law of thermodynamics

(a) heat can’t be transferred from low temperature source to high temperature source

(b) heat can be transferred for low temperature to high temperature source by using refrigeration cycle.

(c) heat can be transferred from low temperature to high temperature source if COP of process is more than unity

(d) heat can’t be transferred from low temperature to high temperature source without the aid of external energy

(e) all of the above.

Answer : d

3. Which of the following laws was formulated by Nernst?

(a)First law of thermodynamics         

(b) Second law of thermodynamics

(c)Third law of thermodynamics         

(d) None of the above

Answer: (c)

 4. Second law of thermodynamics is defined the

(a) Enthalpy                                                                

(b) Entropy 

(c) Internal energy                                                       

(d) Pressure 

Answer: b

5. Heat transfer take place according to ......

(a) Zeroth law of thermodynamics         

(B) First law of thermodynamics 

(c) Second law of thermodynamics         

(d) Third law of thermodynamics 

Answer: c

6. Which law of thermodynamics says that efficiency of a heat engine cannot be 1?

(a)First                                              

(b) zero

(c) second                                           

(d) third

Answer: c

 Hint- entropy change in an Irreversible process has to be positive this means that heat given to an engine cannot be totally converted into work therefore efficiency cannot be 1

7. The second law of thermodynamics states that

(a)  Entropy of an isolated system and never decrease over time

(b) Entropy of a pure crystalline substance at zero kelvin is zero

(c)  Energy is conserved

(d) Entropy of a system can never decrease

 Answer: a

 

 

Multiple Choice Questions Based On Zero and First Laws of Thermodynamics Useful for M.Sc. Entrance, PGT and Different University Exams

 1. Zeroth law of thermodynamics

(a) deals with conversion of mass and energy

(b) deals with reversibility and irreversibility of process

(c) states that if two systems are in equilibrium with a third system, they are in thermal equilibrium with each other

(d) deals with heat engines

Answer : c

2. The basis for measuring thermodynamic property of temperature is given by

(a) zero law of thermodynamics               

(b) first law of thermodynamics

(c) second law of thermodynamics               

(d) third law of thermodynamics

Answer : a

3. The equivalence of two systems in thermal equilibrium is represented by

(a) Temperature                                              (b) Heat

(c) Specific Heat                                               (d) Energy

Answer: a

4. Measurement of temperature is based on

(a) thermodynamic properties                          

(b) zeroth law of thermodynamics

(c) first law of thermodynamics                        

(d) second law of thermodynamics

Answer : b

5. Energy can neither be created nor destroyed but can be converted from one form to other is referred from

(a) zeroth low of thermodynamic                     

(b) first law of thermodynamics

(c) second law to thermodynamics                   

(d) basic law of thermodynamics

Answer : b

6. First law of thermodynamics furnishes the relationship between

(a) heat and work                         

(b) heat, work and properties of the system

(c) various thermodynamic processes             

(d) heat and internal energy

Answer : b

7. According to first law of thermodynamics

(a) work done by a system is equal to heat transferred by the system

(b) total internal energy of a system during a process remains constant

(c) internal energy, enthalpy and entropy during a process remain constant

(d) total energy of a system remains constant

(e) entropy of a system remains constant.

Answer : d

8. First law of thermodynamics

(a) enables to determine change in internal energy of the system

(b) does not help to predict whether the system will or not undergo a change

(c) does not enable to determine change in entropy

(d) provides relationship between heat, work and internal energy

(e) all of the above.

Answer : e

9. According to first law of thermodynamics

(a) mass and energy are mutually convertible  

(b) Carnot engine is most efficient

(c) heat and work are mutually convertible       

(d) mass and light are mutually convertible

(e) heat flows from hot substance to cold substance.

Answer : c

10. Addition of heat at constant pressure to a gas results in

(a) raising its temperature               

(b) raising its pressure

(c) raising its volume                      

(d) raising its temperature and doing external work

(e) doing external work.

Answer : d

11. The first law of thermodynamics is the law of

(a) conservation of mass                                           

(b) conservation of energy

(c) conservation of momentum                                

(d) conservation of heat

Answer : b

 

12. The heat given to an ideal gas in isothermal condition is used

(a) in raising temperature                            (b) in doing external work

(C) in raising temperature and doing external work

(d) in increasing the internal energy

Answer: b

13. For a closed system, the difference between the heat added to the system and the work done by the system is equal to the change in

(a) Enthalpy                                                      (b) Entropy

(c) Temperature                                                (d) Internal Energy

Answer: d

Hint: By First law Q-W=U

14. A thermodynamic process where no heat is exchanged with the surroundings is

(a)  Isothermal                                          

(b) Adiabatic

(c)  Isobaric                                                

(d) Isotropic

Answer: (b)

15. The internal energy of an ideal gas depends only on

(a)Pressure                                                        (b) Volume

(C)Temperature                                                (d) Temperature and Volume Both

Answer: b

16. The internal energy of a real gas depends on

(a)Temperature                                                (b) Volume

(C) Pressure                                                        (d) Temperature and Volume Both

Answer: b

17. Which of the following function is path independent

(a)Work                                                                (b) Heat

(c)Temperature                                                (d) Internal Energy

Answer: d

18.Which thermodynamic process cannot be plotted accurately on thermodynamic coordinates?

a. reversible process                                                    b. irreversible process
c. both reversible and irreversible processes              

d. none of the above

Answer: b

20. The law of expansion or compression of a gas is given by PV to the power n= constant. If n=1 then change is named as

(a)Adiabatic                                                        (b) Isothermal

(c)Isobaric                                                          (d) None of the above

Answer: b

                                      

Multiple Choice Questions Based on Basics of Thermodynamics Useful for M.Sc. Entrance Exam, PGT and Different University Exams

 

1. The unit of temperature in S.I. units is

(a) Centigrade                                                                 (b) Celsius

(c) Fahrenheit                                                                  (d) Kelvin

Answer : d

2. The unit of energy in S.I. units is

(a) watt                                                                       (b) joule

(c) joule/s                                                                    (d) joule/m

Answer : b

3. The unit of pressure in S.I. units is

(a) kg/cm2                                                                   (b) mm of water column

(c) pascal                                                                     (d) dynes per square cm

Answer : c

4. A closed system is one in which

(a) mass does not cross boundaries of the system, though energy may do so

(b) mass crosses the boundary but not the energy

(c) neither mass nor energy crosses the boundaries of the system

(d) both energy and mass cross the boundaries of the system

Answer : a

5. Superheated vapour behaves

(a) exactly as gas                                                 (b) as steam

(c) as ordinary vapour                                        (d) approximately as a gas

Answer : d

6. No liquid can exist as liquid at

(a) – 273 °K                                                                       (b) vacuum

(c) zero pressure                                                               (d) center of earth

Answer : c

 

7. Absolute zero pressure will occur

(a) at sea level                                                             (b) at the center of the earth

(c) when molecular momentum of the system becomes zero

(d) under vacuum conditions                                    (e) at a temperature of – 273 °K

Answer : c

8. The unit of power in S.I. units is

(a) newton                                                                     (b) pascal

(c) watt                                                                          (e) joule.

Answer : c

9. The condition of perfect vacuum, i.e., absolute zero pressure can be attained at

(a) a temperature of – 273.16°C                  (b) a temperature of 0°C

(c) a temperature of 273 °K                         (d) a negative pressure and 0°C temperature

Answer : a

10. Intensive property of a system is one whose value

(a) depends on the mass of the system, like volume

(b) does not depend on the mass of the system, like temperature, pressure, etc.

(c) is not dependent on the path followed but on the state

(d) is dependent on the path followed and not on the state

Answer : b

11. An open system is one in which

(a) mass does not cross boundaries of the system, though energy may do so

(b) neither mass nor energy crosses the boundaries of the system

(c) both energy and mass cross the boundaries of the system

(d) mass crosses the boundary but not the energy

(e) thermodynamic reactions do not occur.

Answer : c

12. Work done in a free expansion process is

(a) + ve                                                                     (b) -ve

(c) zero                                                                      (d) maximum

Answer : c

13. If a gas is heated against a pressure, keeping the volume constant, then work done will be equal to

(a) + v                                                                            (b) – ve

(c) zero                                                                          (d) pressure x volume

Answer : c

14. Which of the following quantities is not the property of the system

(a) pressure                                                                 (b) temperature

(c) specific volume                                                      (d) heat

Answer : d

15. Mixture of ice and water form a

(a) closed system                                                         (b) open system

(c) isolated system                                                       (d) heterogeneous system

Answer : d

16. Which of the following is the property of a system

(a) pressure and temperature                                     (b) internal energy  

(c) volume and density                                                 (d) enthalpy and entropy

(e) all of the above.

Answer : e

17. Which of the following is not the intensive property

(a) pressure                                                                   (b) temperature

(c) density                                                                      (d) heat

Answer : d

18. Extensive property of a system is one whose value

(a) depends on the mass of the system like volume

(b) does not depend on the mass of the system, like temperature, pressure, etc.

(c) is not dependent on the path followed but on the state

(d) is dependent on the path followed and not on the state

(e) is always constant.

Answer : a

19. Which of the following items is not a path function

(a) heat                                                                             (b) work

(c) kinetic energy                                                             (d) VdP

(e) thermal conductivity.

Answer : e

20. Heat and work are

(a) point functions                                                         (b) system properties

(c) path functions                                                           (d) intensive properties

(e) extensive properties.

Answer : c

21. Change in enthalpy of a system is the heat supplied at

(a) constant pressure                                                  (b) constant temperature

(c) constant volume                                                     (d) constant entropy

(e) N.T.P. condition.

Answer : a