# Mechanical Engineering Thermodynamics – Set 14

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## Q1. The efficiency of Diesel cycle increases with

(A) Decrease in cut-off
(B) Increase in cut-off
(C) Constant cut-off
(D) None of these

(A) 12
(B) 14
(C) 16
(D) 32

## Q3. The general gas energy equation is (where Q1 – 2 = Heat supplied, dU = Change in internal energy, and W1 – 2 = Work done in heat units)

(A) Q1 – 2 = dU + W1 – 2
(B) Q1 – 2 = dU – W1 – 2
(C) Q1 – 2 = dU/W1 – 2
(D) Q1 – 2 = dU × W1 – 2

Answer: (A) Q1 – 2 = dU + W1 – 2

## Q4. The sum of internal energy (U) and the product of pressure and volume (p.v) is known as

(A) Work-done
(B) Entropy
(C) Enthalpy
(D) None of these

## Q5. Otto cycle consists of

(A) Two constant volume and two isentropic processes
(B) Two constant pressure and two isentropic processes
(C) Two constant volume and two isothermal processes
(D) One constant pressure, one constant volume and two isentropic processes

Answer: (A) Two constant volume and two isentropic processes

(A) 23.97 bar
(B) 25 bar
(C) 26.03 bar
(D) 34.81 bar

## Q7. Second law of thermodynamics defines

(A) Heat
(B) Work
(C) Internal energy
(D) Entropy

## Q8. The behavior of a perfect gas, undergoing any change in the variables which control physical properties, is governed by

(A) Boyle’s law
(B) Charles’ law
(C) Gay-Lussac law
(D) All of these

(A) 8
(B) 18
(C) 16
(D) 32

## Q10. The throttling process is __ process.

(A) Reversible
(B) Irreversible
(C) Reversible or irreversible
(D) None of these

## Q11. The amount of heat required to raise the temperature of 1 kg of water through one Kelvin is called

(A) Specific heat at constant volume
(B) Specific heat at constant pressure
(C) kilo-Joule
(D) None of these

## Q12. The __ states that change of internal energy of a perfect gas is directly proportional to the change of temperature.

(A) Boyle’s law
(B) Charle’s law
(C) Gay-Lussac law
(D) Joule’s law

## Q13. Which of the following is the correct statement?

(A) For a given compression ratio, both Otto and Diesel cycles have the same efficiency
(B) For a given compression ratio, Otto cycle is more efficient than Diesel cycle
(C) For a given compression ratio, Diesel cycle is more efficient than Otto cycle
(D) The efficiency of Otto or Diesel cycle has nothing to do with compression ratio

Answer: (B) For a given compression ratio, Otto cycle is more efficient than Diesel cycleAnswer: (C) Pulverized coal

## Q14. The fuel mostly used in cement industry and in metallurgical processes is

(A) Wood charcoal
(B) Bituminous coke
(C) Pulverized coal
(D) Coke

## Q15. For the same compression ratio, the efficiency of Diesel cycle is __ Otto cycle.

(A) Greater than
(B) Less than
(C) Equal to
(D) None of these

## Q16. An adiabatic process is one in which

(A) No heat enters or leaves the gas
(B) The temperature of the gas changes
(C) The change in internal energy is equal to the mechanical work-done
(D) All of the above

Answer: (D) All of the above

## Q17. The efficiency of Carnot cycle depends upon

(A) Temperature limits
(B) Pressure ratio
(C) Volume compression ratio
(D) Cut-off ratio and compression ratio

## Q18. The natural solid fuel is

(A) Wood
(B) Coke
(C) Anthracite coal
(D) Pulverized coal

(A) Vapour
(B) Perfect gas
(C) Air
(D) Steam