Mechanical Engineering - Thermodynamics - Basic Concept of Thermodynamics

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Question - 1

Match List I with List II and select the correct answer using the codes given below the lists.

List I List II
P.Work done in a polytropic process 1.\(-\int { vdp } \)
Q. Work done in steady flow process 2.Zero
R. Heat-transfer in a reversiole adiabatic process 3. \(\frac { { p }_{ 1 }{ V }_{ 1 }-{ p }_{ 2 }{ V }_{ 2 } }{ \gamma -1 } \)
S. Work done in an isentropic process 4.\(\frac { { p }_{ 1 }{ V }_{ 1 }-{ p }_{ 2 }{ V }_{ 2 } }{ n-1 } \)
  • A P Q R S 4 1 3 2
  • B P Q R S 1 4 2 3
  • C P Q R S 4 1 2 3
  • D P Q R S 1 2 3 4

Question - 2

The heat transfer Q, the work done Wand the change in internal energy U are all zero in the case of

  • A (a) a rigid vessel containing steam at 150 'C left in the atmosphere which is at 25 oC 
  • B 1kg of gas contained in an insulated cylinder expanding as the piston moves slowly outwards
  • C a rigid vessel containing ammonia gas connected through a valve to an evacuated rigid vessel, the vessel, the valve and the connecting pipes being well insulated and the valve being opened and after a time, condition through the two vessels becoming uniform 
  • D 1 kg of air flowing adiabatically from the atmosphere into a previously evacuated bottle

Question - 3

Zeroth law of thermodynamics states that

  • A two thermodynamic systems are always in thermal equilibrium with each other
  • B if two systems are in thermal equilibrium, then the third system will also be in thermal equilibrium 
  • C two systems not in thermal equilibrium with a third system will also not in thermal equilibrium with each other
  • D when two systems are in thermal equilibrium with a third system, they are in thermal equilibrium with each other

Question - 4

When a system is taken from state A to state B along the path A-C-B, 180 kJ of the heat flows into the system and it does 130 kJ of work (as shown in the figure below).

How much heat will flow into the system along the. path A-D-B, if the work done by it along the path is 40 kJ?

  • A 40 kJ 
  • B 60 kJ
  • C 90 kJ 
  • D 135 kJ

Question - 5

The diagram shown in the figure represents reversible compression of air on the p- V coordinates. The work of compression needed a centrifugal compressor is equal to the area

  • A ABDE-ABC
  • B ABDE
  • C ABFG
  • D ABFG-ABC

Question - 6

Match List I (Process) with List II (Index n in pvn = C) and select the correct answer using the codes given below the lists.

List I List II
P. Adiabatic 1. n = infinity
Q. Isothermal 2. n = Cp/cv
R. Constant pressure 3. n = 1
S. Constant volume 4. n = Cp/ Cv- 1
  5. n = zero
  • A P Q R S 2 3 5 4
  • B P Q R S 2 3 5 1
  • C P Q R S 3 2 1 5
  • D P Q R S 2 5 3 1

Question - 7

Consider the following statements:
1. The first law of thermodynamics is a law of conservation of energy.
2. Perpetual motion machine of the first kind converts energy into equivalent work.
3. A closed system does not exchange work of energy with its surroundings.
4. The second law of thermodynamics stipulates the law of conservation of energy and entropy.
Which of these statements are correct?

  • A 1 and 4
  • B 2 and 4
  • C 2, 3 and 4
  • D 1,2 and 3

Question - 8

The heat absorbed or rejected during a polytropic process is equal to

  • A \({ \left( \frac { \gamma -n }{ \gamma -1 } \right) }^{ 1/2 }\)x work done
  • B \(\left( \frac { \gamma -n }{ \gamma -1 } \right) \)x work done
  • C \(\left( \frac { \gamma -n }{ \gamma -1 } \right) \)x work done
  • D \({ \left( \frac { \gamma -n }{ \gamma -1 } \right) }^{ 2 }\)x work done

Question - 9

In a steady flow adiabatic turbine, the changes in the internal energy, enthalpy, kinetic energy and potential energy of the working fluid from inlet to exit are - 100 kJ/kg, -140 kJ/kg, -10 kJ/kg and zero respectively. Which one of the following gives the amount of work developed by the turbine

  • A 100 kJ/kg 
  • B 110 kJ/kg
  • C 140 kJ/kg 
  • D 150 kJ/kg

Question - 10

170 kJ of heat is supplied to a system at constant volume. Then the system rejects 180 kJ of heat at constant pressure and 40 kJ of work is done on it. The system is finally brought to its original state by adiabatic process. If the initial value of internal energy is 100 kJ, then which one of the following statements is correct?

  • A The highest value of internal energy occurs at the end of the constant volume process 
  • B The highest value of internal energy occurs at the end of constant pressure process
  • C The highest value of internal energy occurs after adiabatic expansion 
  • D Internal energy is equal at all points
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