Which of the following equation is true?
Answer: B
It comes from TdS=dU+pdV and H=U+pV.
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The equation dQ=dU+pdV holds good for
Answer: B
This equation is true only for a reversible(quasi-static) process.
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The rate of entropy increase of the control volume ____ or ____ the net rate of entropy transfer to it.
Answer: B
The difference is the entropy generated within the control volume due to irreversibility.
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This equation is true only for a reversible(quasi-static) process.
Answer: C
This equation holds good for any process undergone by a closed system since it is a relation among properties which are independent of the path.
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When does the entropy of a system become zero?
Answer: B
When thermodynamic probablity W=1, we get S=0 from S=K*lnW and this happens only at T=0K.
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Any thermodynamic process is accompanied by entropy generation
Answer: A
This comes from the second law.
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A process always occurs in such a direction as to cause an increase in the entropy of the universe.
Answer: A
This comes from the second law which indicates the direction in which a process takes place.
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Lost work is given by
Answer: A
The lost work d(LW) indicates the work that is lost due to irreversibility.
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Argon in a light bulb is at 90 kPa and heated from 20°C to 60°C with electrical power. Find the total entropy generation per unit mass of argon.
Answer: C
Energy Eq. : m(u2 – u1) = 1W2 electrical
Entropy Eq.: s2 – s1 = ∫ dq/T + 1s2 gen = 1s2 gen
Process: v = c & ideal gas ∴ P2/ P1 = T2/T1
1s2 gen = s2 – s1 = Cp ln(T2/T1) – R ln (P2/P1)
= Cpln(T2/T1) – R ln(T2/T1) = Cv ln(T2/T1)
= 0.312 ln{(60+273)/(20+273)} = 0.04 kJ/kg K.
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If the first law is the conservation of energy, then the second law is called the law of degradation of energy
Answer: A
Though energy is always conserved but its quality is always degraded.
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