Thermodynamics Questions and Answers – Joule-Kelvin Effect

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This set of Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on “Joule-Kelvin Effect”.

1. When a gas undergoes continuous throttling process by a valve and its pressure and temperature are plotted, then we get a
a) isotherm
b) isenthalpe
c) adiabatic
d) isobar
View Answer

Answer: b
Explanation: All the points plotted on p-T diagram have the same enthaply.
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2. A family of isenthalpes can be obtained for the gas.
a) true
b) false
View Answer

Answer: a
Explanation: The initial pressure and temperature of gas are set to new values and we obtain a family of isenthalpes by throttling to different states.

3. The curve passing through the ____ of the isenthalpes is called the inversion curve.
a) minima
b) maxima
c) both of the mentioned
d) none of the mentioned
View Answer

Answer: b
Explanation: The maxima is considered here for obtaining the inversion curve.
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4. Which of the following statement is true?
a) the value of slope of an isenthalpe on the T-p diagram at any point is called the Joule-Kelvin coefficient
b) the region inside inversion curve is called the cooling region
c) the region outside inversion curve is called the heating region
d) all of the mentioned
View Answer

Answer: d
Explanation: The region depends on the Joule-Kelvin coefficient on the T-p diagram.

5. The locus of all points at which the Joule-Kelvin coefficient is ____ is the inversion curve.
a) negative
b) positive
c) zero
d) infinity
View Answer

Answer: c
Explanation: The inversion curve passes through the maxima of the isenthalpes and the value of Joule-Kelvin coefficient is zero there.
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6. The region inside the inversion curve has ____ Joule-Kelvin coefficient and the region outside the inversion curve has ____ Joule-Kelvin coefficient.
a) positive, positive
b) negative, negative
c) negative, positive
d) positive, negative
View Answer

Answer: d
Explanation: The region having positive Joule-Kelvin coefficient is called the cooling region and the one having negative Joule-Kelvin coefficient is called the heating region.

7. When an ideal gas is made to undergo a Joule-Kelvin expansion, i.e., throttling, there is no change in temperature.
a) true
b) false
View Answer

Answer: a
Explanation: For an ideal gas, the value of Joule-Kelvin coefficient comes out to be zero.
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8. For a gas being throttled, the change in temperature can be
a) positive
b) negative
c) zero
d) all of the mentioned
View Answer

Answer: d
Explanation: The change in temperature depends upon the final pressure after throttling.

9. Maximum temperature drop occurs if the initial state lies ____ the inversion curve.
a) above
b) on
c) below
d) all of the mentioned
View Answer

Answer: b
Explanation: This can be explained from the diagram fro maximum cooling by Joule-Kelvin expansion.
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10. For an ideal gas,
a) volume expansivity = T and Joule-Kelvin coefficient = 0
b) volume expansivity = (1/T) and Joule-Kelvin coefficient = 1
c) volume expansivity = (1/T) and Joule-Kelvin coefficient = 0
d) volume expansivity = T and Joule-Kelvin coefficient = 1
View Answer

Answer: c
Explanation: These values come from the expression for Joule-Kelvin coefficient and pv=RT.

Sanfoundry Global Education & Learning Series – Thermodynamics.
To practice all areas of Thermodynamics, here is complete set of 1000+ Multiple Choice Questions and Answers.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter