Thermodynamics Questions and Answers – Second Law Efficiency-1

This set of Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on “Second Law Efficiency-1”.

1. The first law efficiency is defined as the ratio of the output energy to the input energy.
a) true
b) false
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2. Which of the following statement is true about the first law?
a) it is concerned only with the quantities of energy
b) it disregards the form in which the energy exists
c) it does not discriminate between the energies available at different temperatures
d) all of the mentioned
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3. With the concept of exergy available, which of the following is possible?
a) to analyse means of minimizing the consumption of available energy to perform a given process
b) to ensure most efficient possible conversion of energy
c) both of the mentioned
d) none of the mentioned
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4. Second law efficiency is defined as
a) actual exergy intake / minimum exergy intake
b) minimum exergy intake / actual exergy intake
c) actual exergy intake / maximum exergy intake
d) maximum exergy intake / minimum exergy intake
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5. For a power plant, second law efficiency can be given by desired output(W) / available energy(Wmax).
a) true
b) false
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6. Second law efficiency can also be given as
a) 1 / ( first law efficiency * Carnot efficiency)
b) Carnot efficiency * first law efficiency
c) Carnot efficiency / first law efficiency
d) first law efficiency / Carnot efficiency
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7. If work is involved, Amin= ____ and if heat is involved, Amin= ____
a) w, Q(1+To/T)
b) W, Q(1-To/T)
c) Q(1+To/T), W
d) Q(1-To/T), W
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8. If solar energy Qr is available at a reservoir storage temperature of Tr and if quantity of heat Qa is transferred by the solar collector at temperature Ta, then which of the following is true?
a) first law efficiency = Qa/Qr
b) second law efficiency = exergy output / exergy input
c) second law efficiency = (first law efficiency)*(1-To/Ta)/(1-To/Tr)
d) all of the mentioned
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9. In case of a heat pump, second law efficiency is given as
a) (first law efficiency)*(1-Ta/To)
b) (first law efficiency)*(1+To/Ta)
c) (first law efficiency)*(1-To/Ta)
d) none of the mentioned
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10. Both first law efficiency and second law efficiency indicate how effectively the input has been converted into the product.
a) true
b) false
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11. For proper utilization of exergy, it is desirable to make first law efficiency ____ and the source and use temperatures should ____
a) as close to unity, be different
b) as close to unity, match
c) as close to zero, match
d) as close to zero, be different
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Sanfoundry Global Education & Learning Series – Thermodynamics.
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