# 439 Thermodynamic MCQ For All Mechanical Exams

226)The first TdS equation is

1. a) TdS=Cv*dT + T(∂T/∂p)dV
2. b) TdS=Cv*dT – T(∂p/∂T)dV
3. c) TdS=Cv*dT + T(∂p/∂T)dV
4. d) TdS=Cv*dT – T(∂T/∂p)dV

Ans-C

227)The second TdS equation is

1. a) TdS=Cp*dT + T(∂V/∂T)dp
2. b) TdS=Cp*dT – T(∂V/∂T)dp
3. c) TdS=Cp*dT + T(∂T/∂V)dp
4. d) TdS=Cp*dT – T(∂T/∂V)dp

Ans-B

228)Which of the following is true?

1. a) (∂p/∂V)*(∂V/∂T)*(∂T/∂p)= infinity
2. b) (∂p/∂V)*(∂V/∂T)*(∂T/∂p)= 0
3. c) (∂p/∂V)*(∂V/∂T)*(∂T/∂p)= 1
4. d) (∂p/∂V)*(∂V/∂T)*(∂T/∂p)= -1

Ans-D

229)What do we get on equating the first and second TdS equations?

1. a) Cp-Cv = T*(∂T/∂p)*(∂V/∂T)
2. b) Cp-Cv = T*(∂p/∂T)*(∂V/∂T)
3. c) Cp+Cv = T*(∂p/∂T)*(∂V/∂T)
4. d) none of the mentioned

Ans-B

230)For an ideal gas,

1. a) Cp-Cv = R
2. b) Cp-Cv = mR
3. c) Cp=Cv
4. d) all of the mentioned

Ans-B

231)The volume expansivity and isothermal compressibility is defined as

1. a) volume expansivity = (1/V)*(∂V/∂T) at p and isothermal compressibility = (-1/V)*(∂V/∂T) at T
2. b) volume expansivity = (1/V)*(∂V/∂T) at p and isothermal compressibility = (-1/V)*(∂V/∂T) at T
3. c) volume expansivity = (1/V)*(∂V/∂T) at p and isothermal compressibility = (-1/V)*(∂V/∂T) at T
4. d) none of the mentioned

Ans-B

231)The equation Cp-Cv = -T*(∂p/∂V)(∂V/∂T)2 can also be expressed as

1. a) Cp-Cv = T*V*(isothermal compressibility)2 / (volume expansivity)
2. b) Cp-Cv = T*V*(isothermal compressibility) / (volume expansivity)
3. c) Cp-Cv = T*V*(volume expansivity)2 / (isothermal compressibility)
4. d) Cp-Cv = T*V*(volume expansivity) / (isothermal compressibility)

Ans-C

232)The slope of an isentrope is ____ the slope of an isotherm on p-v diagram.

1. a) less than
2. b) greater than
3. c) equal to
4. d) less than or equal to

Ans-B

233)Which of the following relation gives ɣ .

1. a) 1/(isothermal compressibility *adiabatic compressibility)
2. b) isothermal compressibility * adiabatic compressibility
3. c) adiabatic compressibility / isothermal compressibility
4. d) isothermal compressibility / adiabatic compressibility

Ans-D

234)For a system which undergoes an infinitesimal reversible process between two equilibrium states, the change in internal energy is

1. a) dU = pdV – TdS
2. b) dU = TdS + pdV
3. c) dU = TdS – pdV
4. d) dU = -TdS – pdV

Ans-C

235)The energy equation is given by

1. a) (∂U/∂V) = T*(∂p/∂T) + p
2. b) (∂U/∂V) = T*(∂p/∂T) – p
3. c) (∂U/∂V) = -T*(∂p/∂T) – p
4. d) (∂U/∂V) = p – T*(∂p/∂T

Ans-B

236)Thermal radiation in equilibrium with enclosing walls possesses an energy that depends on volume and temperature.

1. a) true
2. b) false

Ans-A

237)If the temperature is constant, enthaply

1. a) changes with change in p
2. b) changes with change in V
3. c) changes with change in both p and V
4. d) does not change with change in p or V

Ans-D

238)If u is the energy density then pressure(p) exerted by the black-body radiation in an enclosure is

1. a) u/2
2. b) u/3
3. c) u/4
4. d) u

Ans-B

239)The Stefan-Boltzmann law is given by

1. a) u = b*(T2)
2. b) u = b*(T3)
3. c) u = b*(T4)
4. d) u = b*T

Ans-B

240)For a reversible isothermal change of volume, heat to be supplied reversibly to keep temperature constant is given by

1. a) Q = (4/3)b*(T4)*(ΔV)
2. b) Q = (2/3)b*(T2)*(ΔV)
3. c) Q = (1/3)b*(T)*(ΔV)
4. d) none of the mentioned

Ans-A

241)If the temperature is half the original temperature, the volume of black-body radiation is to be ____ adiabatically ____ times its original volume for radiation to remain at equilibrium.

1. a) decreased, four
2. b) decreased, eight
3. c) increased, four
4. d) increased, eight

Ans-D

241)When a gas undergoes continuous throttling process by a valve and its pressure and temperature are plotted, then we get a

1. a) isotherm
2. b) isenthalpe
4. d) isobar

Ans-B

242)A family of isenthalpes can be obtained for the gas.

1. a) true
2. b) false

Ans-A

243)The curve passing through the ____ of the isenthalpes is called the inversion curve.

1. a) minima
2. b) maxima
3. c) both of the mentioned
4. d) none of the mentioned

Ans-B

244)The locus of all points at which the Joule-Kelvin coefficient is ____ is the inversion curve.

1. a) negative
2. b) positive
3. c) zero
4. d) infinity

Ans-C

245)The region inside the inversion curve has ____ Joule-Kelvin coefficient and the region outside the inversion curve has ____ Joule-Kelvin coefficient.

1. a) positive, positive
2. b) negative, negative
3. c) negative, positive
4. d) positive, negative

Ans-D

246)When an ideal gas is made to undergo a Joule-Kelvin expansion, i.e., throttling, there is no change in temperature.

1. a) true
2. b) false

Ans-A

247)For a gas being throttled, the change in temperature can be

1. a) positive
2. b) negative
3. c) zero
4. d) all of the mentioned

Ans-D

248)Maximum temperature drop occurs if the initial state lies ____ the inversion curve.

1. a) above
2. b) on
3. c) below
4. d) all of the mentioned

Ans-B

249)For an ideal gas,

1. a) volume expansivity = T and Joule-Kelvin coefficient = 0
2. b) volume expansivity = (1/T) and Joule-Kelvin coefficient = 1
3. c) volume expansivity = (1/T) and Joule-Kelvin coefficient = 0
4. d) volume expansivity = T and Joule-Kelvin coefficient = 1

Ans-C

250) During phase transitions like vaporization, melting and sublimation

1. a) pressure and temperature remains constant
2. b) volume and entropy changes
3. c) both of the mentioned
4. d) none of the mentioned

Ans-C

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