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This set of Engineering Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on Engineering Thermodynamics Set 7
Q1 | The internal energy of a perfect gas is afunction of
- a) pressure change &temperature
- b) temperature change &specific heat
- c) pressure & work supplied
- d) temperature
Q2 | During a polytropic expansion 25% of heat is converted into work while temperature of gas rises by 30 K, the specific heat of gas at constant volume is
- a) 10% w
- b) 12 % w
- c) 15% w
- d) 20% w
Q3 | During a constant pressure expansion of a gas 33.3 % heat is converted into work while the temperature rises by 20K. The specific heat of gas at constant pressureis
- a) 10% w
- b) 12 % w
- c) 15% w
- d) 20% w
Q4 | During an adiabatic compression when temperature increase by 100% the pressure increases by 1000%. The ratio ofspecific heats, ? is
- a) 1.3
- b) 1.35
- c) 1.4
- d) 1.45
Q5 | In an constant pressure heating certain fraction of heat supplied is converted into work. If ?=1.4 this fraction is
- a) 0.25
- b) 0.286
- c) 0.3
- d) 0.327
Q6 | The area under the curve on temperature entropy diagram represents
- a) work done during the process
- b) heat exchanged during the process
- c) change in internal energy during the process
- d) change in entropy during the process
Q7 | The change in entropy is zero during
- a) hyperbolic process
- b) constant pressureprocess
- c) adiabatic processes
- d) polytropic process
Q8 | Choose incorrect statement
- a) isentropic process is adiabatic
- b) adiabatic process has no heat exchange
- c) hyperbolic process is isothermal
- d) no work is done in constant pressure process
Q9 | Choose the correct statement
- a) there is no change of entropy in an adiabatic expansion
- b) entropy is an extensive property of gas derived from first law of thermodynamics
- c) the area under the curve in a temp.-entropy diagram gives the change of entropy
- d) the change of entropy during a constant pressure process is always negative
Q10 | 1.6 Kg of air is expanded at constant pressure from 100°C to 0°C resulting in entropy change of - 2.0 J/K 3.2 Kg of air is cooled at constant volume from 100°C to 0°C with a change in entropy of -3.0 J/K.The ratio Cp/ Cv is
- a) 1.333
- b) 1.366
- c) 1.4
- d) 1.43
Q11 | Entropy at absolute zero temperature iszero for a
- a) perfect gas
- b) perfect substance
- c) perfect crystal
- d) glass
Q12 | The third law of thermodynamics
- a) defines entropy
- b) provides a base from which entropy is measured
- c) defines change of entropy
- d) gives availability of heat for conversion into work
Q13 | Entropy is called the property of a system because
- a) it has same value at any two equilibrium states
- b) it depends upon the process path
- c) it has a unique value at each equilibrium state
- d) it does not change between two equilibriumstates
Q14 | Entropy of mixture of two gases aftersudden mixing is
- a) greater than
- b) less than its inputtemperature
- c) same as sum of entropy ofindividual gases
- d) unpredictable
Q15 | If a substance goes though a cycle of changes returning back to original state,the change in entropy is
- a) positive
- b) negative
- c) zero
- d) positive or negative depending upon originalstate
Q16 | A sequence of operations which a gas undergoes in such a way that final state issame as original state, mahe a
- a) reversible cycle
- b) irreversible cycle
- c) thermal cycle
- d) thermodynamic cycle
Q17 | In a reversible process
- a) heat transfer takes place over finite temperaturedifference
- b) heat transfer takes place over infinitesimaltemperature difference
- c) heat transfer takes place from surrounding to thesystem
- d) heat transfer takes place from the system tothe surrounding
Q18 | Which of the following processes is very close to reversible
- a) lifting of a body above the ground
- b) compression of a gas in the cylinder against a piston
- c) flow of a fluid in a pipe
- d) motion of a boat in water
Q19 | A perfect gas having p1= 0.1 M/mm², v1=0.18 m³, T1=20°C is compressed to 1/10 of volume in an isothermal process.The change in entropy is
- a) -141.45 j/k
- b) 141.45 j/k
- c) -41446.23 j/k
- d) 0
Q20 | The enthalpy of a system
- a) i= internal energy + pv
- b) i= internal energy + pdv
- c) i= internal energy + vdp
- d) i= change in internalenergy + pv
Q21 | During a polytropic expansion workobtained is 1.8 times the heat transferred. If ?=1.4, n will be
- a) 1.2
- b) 1.19
- c) 1.178
- d) 1.155
Q22 | Which statement is wrong for throttlingexpansion
- a) pressure drop = 0
- b) change in enthalpy = 0
- c) work done = 0
- d) change in internalenergy = 0
Q23 | Which statement is wrong for adiabaticexpansion
- a) h = 0
- b) w = 0
- c) ds = 0
- d) w+e = 0
Q24 | Maximum amount of work that can be converted into heat in any process
- a) depends upon initial & final temperature
- b) depends upon how much work is lost in friction
- c) is 50%
- d) is 100%
Q25 | The universal gas constant will be equal to difference between specific heats at constant pressure & constant volume for
- 1 kg mass of gas
- 1 molecule of gas
- 1 kg molecule of gas
- any mass of gas