Thermodynamics Set 7

Mechanical Engineering

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This set of Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on Thermodynamics Set 7

Q1 | The statement that the entropy of a pure substance in complete theromodynamic equilibrium becomes zero at the absolute zero of temperature is known as
  • First law of thermodynamics
  • Third law of thermodynamics
  • Law of entropy
  • Zeroth law of thermodynamics
  • Second law of thermodynamics
Answer: Third law of thermodynamics
Q2 | A Carnot refrigerator extracts 100 kcal of heat per minute from a cold room which is maintained at - 15?C and it is discharged to atmosphere at 30?C. The horse power required to run the unit would be
  • 1
  • 1.5 to 2
  • Mone than 6
  • 2 to 5
  • 5 to 6
Answer: 1.5 to 2
Q3 | The function of a distributor is
  • To distribute fuel
  • To distribute spark
  • To time the spark
  • To distribute power
  • To generate the spark
Answer: To time the spark
Q4 | A petrol engine fuel that knocks at a low speed
  • Pulsejet
  • will have low fire point
  • has a high octane rating
  • will always knock at high speed
  • may not knock at high speed
Answer: will always knock at high speed
Q5 | Which of the following does not use ambient air for propulsion?
  • Rocket
  • Turboprop
  • Turbojet
  • Pulsojet
  • Propellor
Answer: Rocket
Q6 | During constant pressure heating of a gas the following does not increase?
  • Pressure
  • Pulsejet
  • Volume
  • Entropy
  • Temperature
Answer: Pressure
Q7 | A safety valve is used on boilers to
  • Check the level of water
  • Check the level of steam
  • Check the temperature of steam
  • To release excess pressure
  • None of the above
Answer: To release excess pressure
Q8 | For an ideal gas the value of Joule Kelvin coefficient is
  • Negative
  • Unity
  • Infinite
  • Zero
  • 0.5
Answer: Zero
Q9 | Which of the following cycle consists of two isothemal and two constant volume processes?
  • Joule cycle
  • Stirling cycle
  • Diesel cycle
  • Rankine cycle
  • Otto cycle
Answer: Stirling cycle
Q10 | The statement that energy can be neigher created nor destroyed but only converted from one form to another, is known as
  • Zerothlaw of thermodynamics
  • Second law of thermodynamics
  • First law of theormodynamics
  • Avogadro's hypothesis
  • Kinetic theory of gases
Answer: First law of theormodynamics
Q11 | Avogadro's numbers is
  • 60248.6 x 1026 molecules/(k mol)
  • 6024.86 x 1026 molecules/(k mol)
  • 6.02486 x 1026 molecules/(k mol)
  • 60.2486 x 1026 molecules/(k mol)
  • 602.486 x 1026 molecules/(k mol)
Answer: 6.02486 x 1026 molecules/(k mol)
Q12 | The triple point of a substance is the temperature and pressure at which
  • The solid and liquid phases are in equilibrium
  • The liquid and gaseous phases are in equilibrium
  • The solid, liquid and the gaseous phases are in equilibrium
  • The solid does not melt, the liquid does not boil and the gas does not condense
  • Temperature shows the extent of expansion
Answer: The solid, liquid and the gaseous phases are in equilibrium
Q13 | During the boiling of a liquid, which of the following parameter increases?
  • Temperature
  • Free energy
  • Entropy
  • Heat of vaporisation
  • None of the above
Answer: Entropy
Q14 | Economiser in the boiler heats the
  • Steam
  • Air
  • Feed water
  • Coal
  • None of the above
Answer: Feed water
Q15 | For a closed system, the difference between the heat added to the system and the work done by the system is equal to the change in
  • entropy
  • enthalpy
  • internal energy
  • Pulsejet
  • temperature
Answer: internal energy
Q16 | The area inside the PV diagram for a diesel engine represents
  • heat supplied
  • work done
  • work supplied
  • Pulsejet
  • change in entropy
Answer: work done
Q17 | In case of ideal monoatomic gas, the ratio of specific heats Cp/Cv would be
  • 1
  • 1.67
  • 1.41
  • 1.4
  • 1.33
Answer: 1.67
Q18 | Least value of specific heat
  • Water
  • Ice
  • Alcohol
  • Air
  • Stream
Answer: Air
Q19 | Triple point temperature and pressure for water are
  • 0.1?C and 0.006028 ata
  • 100?C and 1 ata
  • 0.01?C and 0.006028 ata
  • 0?C and 0.1 ata
  • 0?C 1 ata
Answer: 0.01?C and 0.006028 ata
Q20 | The shape of the lid of manhole in a boiler is
  • Circular
  • Elliptical
  • Rectangular
  • Square
  • Special contour
Answer: Elliptical
Q21 | The process in which the change in internal energy of a gas is equal to the work done is known as
  • adiabatic process
  • isochoric process
  • isobaric process
  • isothermal process
  • Pulsejet
Answer: adiabatic process
Q22 | During an adiabatic expansion the increase in volume is associated with
  • Decrease in pressure and decrease in temperature
  • Increase in pressure and decrease in temperature
  • Depends on other factors
  • Increase in pressure and increase in temperature
  • Decrease in pressure and increase in temperature
Answer: Decrease in pressure and decrease in temperature
Q23 | In six stage compression of air set for minimum work conditions
  • Pressure rise per stage will be equal
  • Cylinder volumes will be same
  • The discharge pressure will be six times suction pressure
  • Temperature rise in the cylinders will be the same
  • Work done in successive stages will be in geometrical progression
Answer: Temperature rise in the cylinders will be the same
Q24 | The rate of discharge through the nozzle
  • remains same
  • decreases
  • increases
  • None of the above
Answer: increases
Q25 | A wall 50 mm thick (thermal conductivity k = 40 W/m?C) has temperature difference on two surfaces of 100?C. What could probably change if the temperature difference of this wall drops to 100?C
  • Thickness of wall reduces to 5 mm
  • Thickness of wall increases to 500 mm
  • Thermal conductivity changes to 400 W/?C
  • Rate of heat flow drops to one tenth of the original
  • Area of heat transfer increases 10 times
Answer: Rate of heat flow drops to one tenth of the original
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