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