Mechanical Engineering Thermodynamics – Set 20

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Q1. The standard value of atmospheric pressure taken at sea level is

(A) 1.013 bar
(B) 760 mm of Hg
(C) 1013 × 102 N/m2
(D) All of these

Answer: (D) All of these


Q2. The ultimate analysis of coal consists of the determination of the percentage of

(A) Carbon
(B) Hydrogen and nitrogen
(C) Sulphur and ash
(D) All of these

Answer: (D) All of these


Q3. Steam coal is a

(A) Pulverized coal
(B) Brown coal
(C) Coking bituminous coal
(D) Non-coking bituminous coal

Answer: (D) Non-coking bituminous coal


Q4. The increase in entropy of a system represents

(A) Increase in availability of energy
(B) Increase in temperature
(C) Decrease in pressure
(D) Degradation of energy

Answer: (D) Degradation of energy


Q5. The efficiency of Diesel cycle depends upon

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

Answer: (D) Cut-off ratio and compression ratio


Q6. An isothermal process is governed by

(A) Boyle’s law
(B) Charles’ law
(C) Gay-Lussac law
(D) Avogadro’s law

Answer: (A) Boyle’s law


Q7. The heat supplied to the gas at constant volume is (where m = Mass of gas, cv = Specific heat at constant volume, cp = Specific heat at constant pressure, T2 – T1 = Rise in temperature, and R = Gas constant)

(A) mR (T2 – T1)
(B) mcv (T2 – T1)
(C) mcp (T2 – T1)
(D) mcp (T2 + T1)

Answer: (B) mcv (T2 – T1)


Q8. For the same compression ratio, the efficiency of dual combustion cycle is

(A) Greater than Diesel cycle and less than Otto cycle
(B) Less than Diesel cycle and greater than Otto cycle
(C) Greater than Diesel cycle
(D) Less than Diesel cycle

Answer: (A) Greater than Diesel cycle and less than Otto cycle


Q9. The volumetric or molar specific heat at constant pressure is the product of

(A) Molecular mass of the gas and the specific heat at constant volume
(B) Atomic mass of the gas and the gas constant
(C) Molecular mass of the gas and the gas constant
(D) None of the above

Answer: (D) None of the above


Q10. A process of heating crude oil to a high temperature under a very high pressure to increase the yield of lighter distillates, is known as

(A) Cracking
(B) Carbonization
(C) Fractional distillation
(D) Full distillation

Answer: (A) Cracking


Q11. The oxygen atom is __ times heavier than the hydrogen atom.

(A) 2
(B) 8
(C) 16
(D) 32

Answer: (C) 16


Q12. The heat energy stored in the gas and used for raising the temperature of the gas is known as

(A) External energy
(B) Internal energy
(C) Kinetic energy
(D) Molecular energy

Answer: (B) Internal energy


Q13. The heat absorbed or rejected by the working substance is given by (where ds = Increase or decrease of entropy, T = Absolute temperature, and dQ = Heat absorbed or rejected)

(A) δQ = T.ds
(B) δQ = T/ds
(C) dQ = ds/T
(D) None of these

Answer: (A) δQ = T.ds


Q14. During which of the following process does heat rejection takes place in Carnot cycle?

(A) Isothermal expansion
(B) Isentropic expansion
(C) Isothermal compression
(D) Isentropic compression

Answer: (C) Isothermal compression


Q15. The process is adiabatic, if the value of n in the equation pvn = C, is

(A) Zero
(B) One
(C) γ
(D) ∝

Answer: (C) γ


Q16. The heating of gas at constant volume is governed by

(A) Boyle’s law
(B) Charles’ law
(C) Gay-Lussac law
(D) Avogadro’s law

Answer: (C) Gay-Lussac law


Q17. When a gas is heated at constant pressure

(A) Its temperature will increase
(B) Its volume will increase
(C) Both temperature and volume will increase
(D) Neither temperature not volume will increase

Answer: (C) Both temperature and volume will increase


Q18. A cycle consisting of two isothermal and two isentropic processes, is known as

(A) Carnot cycle
(B) Stirling cycle
(C) Ericsson cycle
(D) Joule cycle

Answer:(A) Carnot cycle


Q19. The efficiency of the Carnot cycle is (where T1 and T2 = Highest and lowest temperature during the cycle)

(A) (T1/T2) – 1
(B) 1 – (T1/T2)
(C) 1 – (T2/T1)
(D) 1 + (T2/T1)

Answer: (C) 1 – (T2/T1)


Q20. A cycle consisting of one constant pressure, one constant volume and two isentropic processes is known as

(A) Carnot cycle
(B) Stirling cycle
(C) Otto cycle
(D) Diesel cycle

Answer: (D) Diesel cycle


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