# Thermodynamics - Mechanical Engineering (MCQ) questions and answers

Dear Readers, Welcome to Thermodynamics multiple choice questions and answers with explanation. These objective type Thermodynamics questions are very important for campus placement test, semester exams, job interviews and competitive exams like GATE, IES, PSU, NET/SET/JRF, UPSC and diploma.

Specially developed for the Mechanical Engineering freshers and professionals, these model questions are asked in the online technical test and interview of many companies.

These tutorial are also important for your viva in university exams like Anna university, Pune, VTU, UPTU, CUSAT etc.

1)   The formation of scale boiler leads to
- Published on 21 Aug 15

a. decrease in efficiency of boiler
b. increase in efficiency of boiler
c. increase in heat transfer
d. decrease in maintenance of boiler
 Answer  Explanation  Related Ques ANSWER: decrease in efficiency of boiler Explanation: No explanation is available for this question!

2)   What is the pH value of water permissible for boiler?
- Published on 21 Aug 15

a. 0
b. 7
c. slightly less than 7
d. slightly more than 7
 Answer  Explanation  Related Ques ANSWER: slightly more than 7 Explanation: No explanation is available for this question!

3)   When the rate of evaporation of water is zero, the relative humidity of the air is
- Published on 21 Aug 15

a. 0%
b. 100%
c. 50%
d. unpredictable
 Answer  Explanation  Related Ques ANSWER: 100% Explanation: No explanation is available for this question!

4)   When,
H1 = Total heat of air entering the coil (heating or cooling)
H2 = Total heat of air leaving the coil (heating or cooling)
H3 = Total heat of air at the end of the process (humidification or dehumidification)
then, the sensible heat factor (H2 – H1) / (H3 – H1) represents the process of

- Published on 21 Aug 15

a. cooling and humidification
b. cooling and dehumidification
c. heating and humidification
d. heating and dehumidification
 Answer  Explanation  Related Ques ANSWER: heating and humidification Explanation: No explanation is available for this question!

5)   The dew point temperature is less than the wet bulb temperature for
- Published on 21 Aug 15

a. saturated air
b. unsaturated air
c. both saturated and unsaturated air
d. none of the above
 Answer  Explanation  Related Ques ANSWER: unsaturated air Explanation: No explanation is available for this question!

6)   At 100% relative humidity, the wet bulb temperature is
- Published on 21 Aug 15

a. lower than the dew point temperature
b. higher than the dew point temperature
c. equal to the dew point temperature
d. none of the above
 Answer  Explanation  Related Ques ANSWER: equal to the dew point temperature Explanation: No explanation is available for this question!

7)   What is the perfect condition for dehumidification of air?
- Published on 21 Aug 15

a. air is heated above its dew point temperature
b. air is cooled up to its dew point temperature
c. air is heated below its dew point temperature
d. air is cooled below its dew point temperature
 Answer  Explanation  Related Ques ANSWER: air is cooled below its dew point temperature Explanation: No explanation is available for this question!

8)   The gas-refrigeration system is
- Published on 21 Aug 15

a. more heavy and bulky than the vapour compression cycle
b. less heavy and bulky than the vapour compression cycle
c. same in construction with the vapour compression cycle
d. none of the above
 Answer  Explanation  Related Ques ANSWER: less heavy and bulky than the vapour compression cycle Explanation: No explanation is available for this question!

9)   How is the COP of gas-refrigeration cycle compared with the COP of vapour compression cycle, for the same capacity?
- Published on 21 Aug 15

a. the COP of gas-refrigeration cycle is lower than the COP of vapour compression cycle, for the same capacity
b. the COP of gas-refrigeration cycle is higher than the COP of vapour compression cycle, for the same capacity
c. the COP of gas-refrigeration cycle is same as the COP of vapour compression cycle
d. none of the above
 Answer  Explanation  Related Ques ANSWER: the COP of gas-refrigeration cycle is lower than the COP of vapour compression cycle, for the same capacity Explanation: No explanation is available for this question!

10)   What is the relation between brake efficiency, internal efficiency and mechanical efficiency?
- Published on 21 Aug 15

a. ηInternal = ηMech * ηBrake
b. ηMech = ηInternal * ηBrake
c. ηBrake = ηInternal * ηMech
d. none of the above
 Answer  Explanation  Related Ques ANSWER: ηBrake = ηInternal * ηMech Explanation: No explanation is available for this question!

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