Mechanical Engineering Thermodynamics – Set 11

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Q1. Molecular volume of any perfect gas at 600 × 103 N/m² and 27°C will be

(A) 4.17 m3/kg mol
(B) 400 m3/kg mol
(C) 0.15 m3/kg mol
(D) 41.7 m3/kg mol

Answer: (A) 4.17 m3/kg mol


Q2. First law of thermodynamics

(A) Enables to determine change in internal energy of the system
(B) Does not enable to determine change in entropy
(C) Provides relationship between heat, work and internal energy
(D) All of the above

Answer: (D) All of the above


Q3. The efficiency of Diesel cycle depends upon

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

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


Q4. Kelvin Planck’s law deals with

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

Answer: (C) Conversion of heat into work


Q5. An open system is one in which

(A) Mass does not cross boundaries of the system, though energy may do so
(B) Neither mass nor energy crosses the boundaries of the system
(C) Both energy and mass cross the boundaries of the system
(D) Mass crosses the boundary but not the energy

Answer: (C) Both energy and mass cross the boundaries of the system


Q6. The value of the product of molecular weight and the gas characteristic constant for all the gases in S.I. units is

(A) 29.27 J/kmol °K
(B) 83.14 J/kmol °K
(C) 848 J/kmol °K
(D) 735 J/kmol °K

Answer: (B) 83.14 J/kmol °K


Q7. The energy of molecular motion appears as

(A) Heat
(B) Potential energy
(C) Surface tension
(D) Friction

Answer: (A) Heat


Q8. Diesel cycle consists of following four processes

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

Answer: (C) Two isentropic, one constant volume and one constant pressure


Q9. The ideal efficiency of a Brayton cycle with regeneration, with increase in pressure ratio will

(A) Increase
(B) Decrease
(C) Remain unchanged
(D) Increase/decrease depending on application

Answer:(B) Decrease


Q10. The unit of energy in S.I. units is

(A) watt
(B) Joule
(C) joule/s
(D) joule/m

Answer: (B) Joule


Q11. Otto cycle is also known as

(A) Constant pressure cycle
(B) Constant volume cycle
(C) Constant temperature cycle
(D) Constant temperature and pressure cycle

Answer: (B) Constant volume cycle


Q12. The condition for the reversibility of a cycle is

(A) The pressure and temperature of the working substance must not differ, appreciably, from those of the surroundings at any stage in the process
(B) All the processes, taking place in the cycle of operation, must be extremely slow
(C) The working parts of the engine must be friction free
(D) All of the above

Answer: (D) All of the above


Q13. Properties of substances like pressure, temperature and density, in thermodynamic coordinates are

(A) Path functions
(B) Point functions
(C) Cyclic functions
(D) Real functions

Answer: (B) Point functions


Q14. The total energy of a molecule is shared equally by the various degrees of freedom possessed by it. This law is known as

(A) Law of equipartition of energy
(B) Law of degradation of energy
(C) Law of conservation of energy
(D) None of these

Answer: (A) Law of equipartition of energy


Q15. On volume basis, air contains following parts of oxygen

(A) 21
(B) 23
(C) 25
(D) 77

Answer: (A) 21


Q16. A gas is compressed in a cylinder by a movable piston to a volume one half its original volume. During the process 300 kJ heat left the gas and internal energy remained same. The work done on gas in Nm will be

(A) 300 Nm
(B) 300,000 Nm
(C) 30 Nm
(D) 3000 Nm

Answer:(B) 300,000 Nm


Q17. Addition of heat at constant pressure to a gas results in

(A) Raising its temperature
(B) Raising its pressure
(C) Raising its volume
(D) Raising its temperature and doing external work

Answer: (D) Raising its temperature and doing external work


Q18. The door of a running refrigerator inside a room was left open. Which of the following statements is correct?

(A) The room will be cooled to the temperature inside the refrigerator
(B) The room will be cooled very slightly
(C) The room will be gradually warmed up
(D) The temperature of the air in room will remain unaffected

Answer: (C) The room will be gradually warmed up


Q19. 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-third
(B) Three-forth
(C) One-half
(D) Two-third

Answer: (D) Two-third


Q20. The hyperbolic process is governed by

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

Answer: (B) Boyle’s law


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