21. The area under the temperature-entropy curve (T – s curve) of any thermodynamic process represents
heat absorbed
heat rejected
either (a) or (b)
none of these
✅ The correct answer is option C.
Thermodynamics MCQs
22. The greater the pressure difference in throttling, the lesser is the irreversibility.
Yes
No
✅ The correct answer is option B.
23. The expansion ratio (r) is the ratio of (where v1 = Volume at the beginning of expansion, and v2 = Volume at the end of expansion)
✅ The correct answer is option B.
24. A cycle consisting of __________ and two isothermal processes is known as Stirling cycle.
two constant pressure
two constant volume
two isentropic
one constant pressure,
✅ The correct answer is option B.
25. The condition for the reversibility of a cycle is
the pressure and temperature of the working substance must not differ, appreciably, from those of the surroundings at any stage in the process
all the processes, taking place in the cycle of operation, must be extremely slow
the working parts of the engine must be friction free
all of the above
✅ The correct answer is option D.
26. The fuel mostly used in cement industry and in metallurgical processes is
wood charcoal
bituminous coke
pulverised coal
coke
✅ The correct answer is option C.
27. Which of the following is the correct statement of the second law of thermodynamics?
It is impossible to construct an engine working on a cyclic process, whose sole purpose is to convert heat energy into work.
It is impossible to transfer heat from a body at a lower temperature to a higher temperature, without the aid of an external source.
There is a definite amount of mechanical energy, which can be obtained from a given quantity of heat energy.
all of the above
✅ The correct answer is option D.
28. A machine which violates the first law of thermodynamics is known as perpetual motion machine of the second kind.
Correct
Incorrect
✅ The correct answer is option B.
29. Petrol is distilled at
65° to 220°C
220° to 345°C
345° to 470°C
470° to 550°C
✅ The correct answer is option A.
30. The heating of gas at constant volume is governed by
Boyle’s law
Charles’ law
Gay-Lussac law
Avogadro’s law
✅ The correct answer is option C.