Thermodynamics Questions and Answers – Comments on Exergy

This set of Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on “Comments on Exergy”.

1. ____ is conserved but ____ is not conserved.
a) exergy, energy
b) energy, exergy
c) both exergy and energy are conserved
d) neither exergy nor energy is conserved
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2. Exergy is a composite property.
a) true
b) false
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3. A dead state
a) is in equilibrium with its surroundings
b) has zero exergy
c) both of the mentioned
d) none of the mentioned
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4. Which of the following statement is true?
a) KE is entirely available energy
b) PE is entirely exergy
c) The exergy of thermal energy of reservoirs is equivalent to the work output of a Carnot engine operating between the reservoir at temperature T and environment To.
d) all of the mentioned
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5. Useful work is given by
a) difference between the actual work and the surrounding work
b) W – W for surroundings
c) W – p(V2-V1)
d) all of the mentioned
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6. The surrounding work is zero for
a) cyclic devices
b) steady flow devices
c) system with fixed boundaries
d) all of the mentioned
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7. The maximum amount of useful work that can be obtained from a system as it undergoes a process between two specified states is called
a) adiabatic work
b) reversible work
c) irreversible work
d) none of the mentioned
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8. If the final state of the system is the dead state, the ____ and the ____ become identical.
a) reversible work, exergy
b) irreversible work, exergy
c) reversible work, irreversible work
d) none of the mentioned
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9. The difference between the reversible work and the useful work for a process is called irreversibility.
a) true
b) false
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10. For a total reversible process,
a) W reversible = useful work
b) irreversibility = 0
c) both of the mentioned
d) none of the mentioned
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11. Two engines having same thermal efficiency but supplied with heat from source at different temperatures,
a) will convert same fraction of heat they receive into work
b) from second law, one will perform better than other
c) this can be considered as a deficiency of the first law
d) all of the mentioned
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12. Second law efficiency is defined as the ratio of actual thermal efficiency to the maximum possible thermal efficiency.
a) true
b) false
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13. Which of the following is true?
a) for work producing devices, second law efficiency = useful work / reversible work
b) for work absorbing devices, second law efficiency = reversible work / useful work
c) both of the mentioned
d) none of the mentioned
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14. In the context of first law efficiency and second law efficiency, which of the following statement is true?
a) first law efficiency = energy output / energy input and their difference is the energy loss
b) second law efficiency = exergy output / exergy input and their difference is irreversibility
c) by reducing energy loss, first law efficiency can be reduced and by reducing irreversibilities, second law efficiency can be reduced
d) all of the mentioned
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Sanfoundry Global Education & Learning Series – Thermodynamics.
To practice all areas of Thermodynamics, here is complete set of 1000+ Multiple Choice Questions and Answers.