Mechanical Engineering Thermodynamics – Set 17

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Q1. When two bodies are in thermal equilibrium with a third body, they are also in thermal equilibrium with each other. This statement is called

(A) Zeroth law of thermodynamics
(B) First law of thermodynamics
(C) Second law of thermodynamics
(D) Kelvin Planck’s law

Answer: (A) Zeroth law of thermodynamics


Q2. Carbonization of coal consists of

(A) Drying and crushing the coal to a fine powder
(B) Moulding the finely ground coal under pressure with or without a binding material
(C) Heating the wood with a limited supply of air to temperature not less than 280°C
(D) None of the above

Answer: (D) None of the above


Q3. According to Kelvin-Planck’s statement of second law of thermodynamics,

(A) It is impossible to construct an engine working on a cyclic process, whose sole purpose is to convert heat energy into work
(B) It is possible to construct an engine working on a cyclic process, whose sole purpose is to convert heat energy into work
(C) It is impossible to construct a device which operates in a cyclic process and produces no effect other than the transfer of heat from a cold body to a hot body
(D) None of the above

Answer: (A) It is impossible to construct an engine working on a cyclic process, whose sole purpose is to convert heat energy into work


Q4. A process, in which the working substance neither receives nor gives out heat to its surroundings during its expansion or compression, is called

(A) Isothermal process
(B) Hyperbolic process
(C) Adiabatic process
(D) Polytropic process

Answer: (C) Adiabatic process


Q5. The efficiency of Ericsson cycle is __ Carnot cycle.

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

Answer: (C) Equal to


Q6. A series of operations, which takes place in a certain order and restore the initial conditions at the end, is known as

(A) Reversible cycle
(B) Irreversible cycle
(C) Thermodynamic cycle
(D) None of these

Answer: (C) Thermodynamic cycle


Q7. The value of one bar (in S. I. units) is equal to

(A) 1 × 102 N/m2
(B) 1 × 103 N/m2
(C) 1 × 104 N/m2
(D) 1 × 105 N/m2

Answer: (D) 1 × 105 N/m2


Q8. The amount of heat generated per kg of fuel is known as

(A) Calorific value
(B) Heat energy
(C) Lower calorific value
(D) Higher calorific value

Answer: (A) Calorific value


Q9. The kinetic energy per kg molecule of any gas at absolute temperature T is equal to (where Ru = Universal gas constant)

(A) Ru × T
(B) 1.5 Ru × T
(C) 2 Ru × T
(D) 3 Ru × T

Answer: (B) 1.5 Ru × T


Q10. For the same maximum pressure and temperature,

(A) Otto cycle is more efficient than Diesel cycle
(B) Diesel cycle is more efficient than Otto cycle
(C) Dual cycle is more efficient than Otto and Diesel cycles
(D) Dual cycle is less efficient than Otto and Diesel cycles

Answer: (B) Diesel cycle is more efficient than Otto cycle


Q11. Work-done during adiabatic expansion is given by (where p1 v1, T1 = Pressure, volume and temperature for the initial condition of gas, p2, v2, T2 = Corresponding values for the final condition of gas, R = Gas constant, and γ = Ratio of specific heats)

(A) (p1 v1 – p2, v2)/(γ – 1)
(B) [m R (T1 – T2)] /(γ – 1)
(C) [m R T1/(γ – 1)][1 – (p2, v2 /p1 v1)]
(D) All of these

Answer: (D) All of these


Q12. The absolute zero temperature is taken as

(A) -273°C
(B) 73°C
(C) 237°C
(D) -237°C

Answer: (A) -273°C


Q13. In S. I. units, the value of the universal gas constant is

(A) 8.314 J/kg mole-K
(B) 83.14 J/kgmole-K
(C) 831.4 J/kgmole-K
(D) 8314 J/kgmole-K

Answer: (D) 8314 J/kgmole-K


Q14. The absolute zero pressure will be

(A) When molecular momentum of the system becomes zero
(B) At sea level
(C) At the temperature of – 273 K
(D) At the center of the earth

Answer: (A) When molecular momentum of the system becomes zero


Q15. Which of the following has the highest calorific value?

(A) Peat
(B) Lignite
(C) Bituminous coal
(D) Anthracite coal

Answer: (D) Anthracite coal


Q16. The area under the temperature-entropy curve (T – s curve) of any thermodynamic process represents

(A) Heat absorbed
(B) Heat rejected
(C) Either (A) or (B)
(D) None of these

Answer: (C) Either (A) or (B)


Q17. The pressure exerted by an ideal gas is __ of the kinetic energy of all the molecules contained in a unit volume of gas.

(A) One-half
(B) One-third
(C) Two-third
(D) Three-fourth

Answer: (C) Two-third


Q18. The ratio of specific heat at constant pressure (cp) and specific heat at constant volume (cv) is always __ one.

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

Answer: (C) Greater than


Q19. The mass of excess air supplied is equal to

(A) (23/100) × Mass of excess carbon
(B) (23/100) × Mass of excess oxygen
(C) (100/23) × Mass of excess carbon
(D) (100/23) × Mass of excess oxygen

Answer: (D) (100/23) × Mass of excess oxygen


Q20. The compression ratio for petrol engines is

(A) 3 to 6
(B) 5 to 8
(C) 15 to 20
(D) 20 to 30

Answer: (B) 5 to 8


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