Mechanical Engineering Thermodynamics – Set 13

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Q1. The heat and mechanical energies are mutually convertible. This statement was established by

(A) Boyle
(B) Charles
(C) Joule
(D) None of these

Answer:(C) Joule


Q2. The general law of expansion or compression is pvn = C, The process is said to be hyperbolic, if n is equal to

(A) 0
(B) 1
(C) γ
(D) ∝

Answer: (B) 1


Q3. When the gas is heated at constant pressure, the heat supplied

(A) Increases the internal energy of the gas
(B) Increases the temperature of the gas
(C) Does some external work during expansion
(D) Both (B) and (C)

Answer: (D) Both (B) and (C)


Q4. First law of thermodynamics deals with

(A) Conservation of heat
(B) Conservation of momentum
(C) Conservation of mass
(D) Conservation of energy

Answer: (D) Conservation of energy


Q5. The entropy of water at 0°C is assumed to be

(A) 1
(B) 0
(C) -1
(D) 10

Answer:(B) 0


Q6. Which of the following gas has a minimum molecular mass?

(A) Oxygen
(B) Nitrogen
(C) Hydrogen
(D) Methane

Answer: (C) Hydrogen


Q7. A cycle consisting of two constant pressure and two isentropic processes is known as

(A) Carnot cycle
(B) Stirling cycle
(C) Otto cycle
(D) None of these

Answer: (D) None of these


Q8. Which of the following is correct?

(A) Absolute pressure = Gauge pressure + Atmospheric pressure
(B) Gauge pressure = Absolute pressure + Atmospheric pressure
(C) Atmospheric pressure = Absolute pressure + Gauge pressure
(D) Absolute pressure = Gauge pressure – Atmospheric pressure

Answer: (A) Absolute pressure = Gauge pressure + Atmospheric pressure


Q9. The most probable velocity of the gas molecules is given by

(A) √(KT/m)
(B) √(2KT/m)
(C) √(3KT/m)
(D) √(5KT/m)

Answer: (B) √(2KT/m)


Q10. When the gas is cooled at constant pressure,

(A) Its temperature increases but volume decreases
(B) Its volume increases but temperature decreases
(C) Both temperature and volume increases
(D) Both temperature and volume decreases

Answer: (D) Both temperature and volume decreases


Q11. The principal constituents of a fuel are

(A) Carbon and hydrogen
(B) Oxygen and hydrogen
(C) Sulphur and oxygen
(D) Sulphur and hydrogen

Answer: (A) Carbon and hydrogen


Q12. Kelvin-Planck’s law deals with

(A) Conservation of work
(B) Conservation of heat
(C) Conversion of heat into work
(D) Conversion of work into heat

Answer: (C) Conversion of heat into work


Q13. The efficiency of Diesel cycle approaches to Otto cycle efficiency when

(A) Cut-off is increased
(B) Cut-off is decreased
(C) Cut-off is zero
(D) Cut-off is constant

Answer: (C) Cut-off is zero


Q14. When cut-off ratio is __ the efficiency of Diesel cycle approaches to Otto cycle efficiency.

(A) Zero
(B) 1/5
(C) 4/5
(D) 1

Answer: (A) Zero


Q15. The change of entropy, when heat is absorbed by the gas, is

(A) Positive
(B) Negative
(C) Positive or negative
(D) None of these

Answer: (A) Positive


Q16. The heat and work are mutually convertible. This statement is called __ law of thermodynamics.

(A) Zeroth
(B) First
(C) Second
(D) Third

Answer:(B) First


Q17. One kilowatt is equal to

(A) 1 N-m/s
(B) 100 N-m
(C) 1000 N-m/s
(D) 1 × 106 N-m/s

Answer: (C) 1000 N-m/s


Q18. When a gas is heated at constant volume

(A) Its temperature will increase
(B) Its pressure will increase
(C) Both temperature and pressure will increase
(D) Neither temperature nor pressure will increase

Answer: (C) Both temperature and pressure will increase


Q19. The value of cp/cv for air is

(A) 1
(B) 1.4
(C) 1.45
(D) 2.3

Answer: (B) 1.4


Q20. Producer gas is obtained by

(A) Partial combustion of coal, coke, anthracite coal or charcoal in a mixed air steam blast
(B) Carbonization of bituminous coal
(C) Passing steam over incandescent coke
(D) Passing air and a large amount of steam over waste coal at about 650°C

Answer: (A) Partial combustion of coal, coke, anthracite coal or charcoal in a mixed air steam blast


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