Question 1

On a warm day a pool of water transfers energy to the air as heat and freezes.This is a direct violation of:

Accepted Answer

A) the zeroth law of thermodynamics 
B) the first law of thermodynamics 
C) the second law of thermodynamics 
D) the third law of thermodynamics 
E) none of the above 
A) the zeroth law of thermodynamics 
B) the first law of thermodynamics 
C) the second law of thermodynamics 
D) the third law of thermodynamics 
E) none of the above C

Question 2

A force of 5 N stretches an elastic band at room temperature.The rate at which its entropy changes as it stretches is about:

Accepted Answer

A) -2 x 10-2 J/K·m 
B) 2 x 10-2 J/K·m 
C) 1500 J/K·m 
D) -1500 J/K·m 
E) cannot be calculated without knowing the heat capacity 
A) -2 x 10-2 J/K·m 
B) 2 x 10-2 J/K·m 
C) 1500 J/K·m 
D) -1500 J/K·m 
E) cannot be calculated without knowing the heat capacity A

Question 3

An ideal gas is to taken reversibly from state i, at temperature T1, to other states labeled I, II, III, IV and V on the p-V diagram below.All are at the same temperature T2. Rank the five processes according to the change in entropy of the gas, least to greatest.

Accepted Answer

A) I, II, III, IV, V 
B) V, IV, III, II, I 
C) I, then II, III, IV, and V tied 
D) I, II, III, and IV, tied, then V 
E) I and V tied, then II, III, IV 
A) I, II, III, IV, V 
B) V, IV, III, II, I 
C) I, then II, III, IV, and V tied 
D) I, II, III, and IV, tied, then V 
E) I and V tied, then II, III, IV A

Question 4

A Carnot heat engine runs between a cold reservoir at temperature TL and a hot reservoir at temperature TH.You want to increase its efficiency.Of the following, which change results in the greatest increase in efficiency? The value of $\Delta$T is the same for all changes.

Accepted Answer

A) Raise the temperature of the hot reservoir by $\Delta$T 
B) Raise the temperature of the cold reservoir by $\Delta$T 
C) Lower the temperature of the hot reservoir by $\Delta$T 
D) Lower the temperature of the cold reservoir by $\Delta$T 
E) Lower the temperature of the hot reservoir by (1/2)$\Delta$T and raise the temperature of the cold reservoir by (1/2)$\Delta$T 
A) Raise the temperature of the hot reservoir by $\Delta$T 
B) Raise the temperature of the cold reservoir by $\Delta$T 
C) Lower the temperature of the hot reservoir by $\Delta$T 
D) Lower the temperature of the cold reservoir by $\Delta$T 
E) Lower the temperature of the hot reservoir by (1/2)$\Delta$T and raise the temperature of the cold reservoir by (1/2)$\Delta$T

Question 5

Possible units of entropy are:

Accepted Answer

A) J 
B) J/K 
C) J-1 
D) liter.atm 
E) cal/mol 
A) J 
B) J/K 
C) J-1 
D) liter.atm 
E) cal/mol

Question 6

A hot object and a cold object are placed in thermal contact and the combination is isolated.They transfer energy until they reach a common temperature.The change $\Delta$Sh in the entropy of the hot object, the change $\Delta$Sc in the entropy of the cold object, and the change $\Delta$Stotal in the entropy of the combination are:

Accepted Answer

A) "$\Delta$Sh > 0, $\Delta$Sc > 0, $\Delta$Stotal > 0" B) "$\Delta$Sh c > 0, $\Delta$Stotal > 0" C) "$\Delta$Sh c > 0, $\Delta$Stotal h > 0, $\Delta$Sc total > 0" E) "$\Delta$Sh > 0, $\Delta$Sc total < 0" A) "$\Delta$Sh > 0, $\Delta$Sc > 0, $\Delta$Stotal > 0" B) "$\Delta$Sh c > 0, $\Delta$Stotal > 0" C) "$\Delta$Sh c > 0, $\Delta$Stotal h > 0, $\Delta$Sc total > 0" E) "$\Delta$Sh > 0, $\Delta$Sc total < 0"

Question 7

For a system of molecules,

Accepted Answer

A) each configuration is equally probable. 
B) microstates with more configurations are more probable than other microstates. 
C) configurations with more microstates are more probable than other configurations. 
D) microstates with more configurations are less probable than other microstates. 
E) configurations with more microstates are less probable than other configurations. 
A) each configuration is equally probable. 
B) microstates with more configurations are more probable than other microstates. 
C) configurations with more microstates are more probable than other configurations. 
D) microstates with more configurations are less probable than other microstates. 
E) configurations with more microstates are less probable than other configurations.

Question 8

An ideal gas, consisting of n moles, undergoes a reversible isothermal process during which the volume changes from Vi to Vf.The change in entropy of the thermal reservoir in contact with the gas is given by:

Accepted Answer

A) nR(Vf - Vi) 
B) nR ln(Vf - Vi) 
C) nR ln(Vi/Vf) 
D) nR ln(Vf/Vi) 
E) none of the above (entropy can't be calculated for the thermal reservoir) 
A) nR(Vf - Vi) 
B) nR ln(Vf - Vi) 
C) nR ln(Vi/Vf) 
D) nR ln(Vf/Vi) 
E) none of the above (entropy can't be calculated for the thermal reservoir)

Question 9

A heat engine in each cycle absorbs energy from a reservoir as heat and does an equivalent amount of work, with no other changes.This engine violates:

Accepted Answer

A) the zeroth law of thermodynamics 
B) the first law of thermodynamics 
C) the second law of thermodynamics 
D) the third law of thermodynamics 
E) none of the above 
A) the zeroth law of thermodynamics 
B) the first law of thermodynamics 
C) the second law of thermodynamics 
D) the third law of thermodynamics 
E) none of the above

Question 10

An inventor claims to have a heat engine that has efficiency of 40% when it operates between a high temperature reservoir of 150$\degree$C and a low temperature reservoir of 30$\degree$C.This engine:

Accepted Answer

A) must violate the zeroth law of thermodynamics 
B) must violate the first law of thermodynamics 
C) must violate the second law of thermodynamics 
D) must violate the third law of thermodynamics 
E) does not necessarily violate any of the laws of thermodynamics 
A) must violate the zeroth law of thermodynamics 
B) must violate the first law of thermodynamics 
C) must violate the second law of thermodynamics 
D) must violate the third law of thermodynamics 
E) does not necessarily violate any of the laws of thermodynamics

Question 11

In a reversible process the system:

Accepted Answer

A) is always close to equilibrium states 
B) is close to equilibrium states only at the beginning and end 
C) might never be close to any equilibrium state 
D) is close to equilibrium states throughout, except at the beginning and end 
E) is none of the above 
A) is always close to equilibrium states 
B) is close to equilibrium states only at the beginning and end 
C) might never be close to any equilibrium state 
D) is close to equilibrium states throughout, except at the beginning and end 
E) is none of the above

Question 12

A heat engine in each cycle absorbs energy of magnitude $\vert$QH $\vert$ as heat from a high temperature reservoir, does work of magnitude F$\vert$W $\vert$, and then absorbs energy of magnitude $\vert$QL $\vert$ as heat from a low temperature reservoir.If $\vert$W $\vert$ = $\vert$QH $\vert$ + $\vert$QL $\vert$this engine violates:

Accepted Answer

A) the zeroth law of thermodynamics 
B) the first law of thermodynamics 
C) the second law of thermodynamics 
D) the third law of thermodynamics 
E) none of the above 
A) the zeroth law of thermodynamics 
B) the first law of thermodynamics 
C) the second law of thermodynamics 
D) the third law of thermodynamics 
E) none of the above

Question 13

For all irreversible processes involving a system and its environment:

Accepted Answer

A) the entropy of the system does not change 
B) the entropy of the system increases 
C) the total entropy of the system and its environment does not change 
D) the total entropy of the system and its environment increases 
E) none of the above 
A) the entropy of the system does not change 
B) the entropy of the system increases 
C) the total entropy of the system and its environment does not change 
D) the total entropy of the system and its environment increases 
E) none of the above

Question 14

According to the second law of thermodynamics:

Accepted Answer

A) all heat engines have the same efficiency 
B) all reversible heat engines have the same efficiency 
C) the efficiency of any heat engine is independent of its working substance 
D) the efficiency of a Carnot engine depends only on the temperatures of the two reservoirs 
E) all Carnot engines theoretically have 100% efficiency 
A) all heat engines have the same efficiency 
B) all reversible heat engines have the same efficiency 
C) the efficiency of any heat engine is independent of its working substance 
D) the efficiency of a Carnot engine depends only on the temperatures of the two reservoirs 
E) all Carnot engines theoretically have 100% efficiency

Question 15

Let k be the Boltzmann constant.If the configuration of the molecules in a gas changes so that the multiplicity is reduced to one-third its previous value, the entropy of the gas changes by:

Accepted Answer

A) "$\Delta$S = 0" 
B) "$\Delta$S = 3k ln 2" 
C) "$\Delta$S = -3k ln 2" 
D) "$\Delta$S = k ln(1/3)" 
E) "$\Delta$S = -3 ln 3" 
A) "$\Delta$S = 0" 
B) "$\Delta$S = 3k ln 2" 
C) "$\Delta$S = -3k ln 2" 
D) "$\Delta$S = k ln(1/3)" 
E) "$\Delta$S = -3 ln 3"

Question 16

Which of the following is NOT a state variable?

Accepted Answer

A) Work 
B) Internal energy 
C) Entropy 
D) Temperature 
E) Pressure 
A) Work 
B) Internal energy 
C) Entropy 
D) Temperature 
E) Pressure

Question 17

A Carnot cycle heat engine operates between 400 K and 500 K.Its efficiency is:

Accepted Answer

A) 20% 
B) 25% 
C) 44% 
D) 80% 
E) 100% 
A) 20% 
B) 25% 
C) 44% 
D) 80% 
E) 100%

Question 18

Consider all possible isothermal contractions of an ideal gas.The entropy of the gas:

Accepted Answer

A) does not change for any of them 
B) does not decrease for any of them 
C) does not increase for any of them 
D) increases for all of them 
E) decreases for all of them 
A) does not change for any of them 
B) does not decrease for any of them 
C) does not increase for any of them 
D) increases for all of them 
E) decreases for all of them

Question 19

A Carnot refrigerator runs between a cold reservoir at temperature TL and a hot reservoir at temperature TH.You want to increase its coefficient of performance.Of the following, which change results in the greatest increase in the coefficient? The value of $\Delta$T is the same for all changes.

Accepted Answer

A) Raise the temperature of the hot reservoir by $\Delta$T 
B) Raise the temperature of the cold reservoir by $\Delta$T 
C) Lower the temperature of the hot reservoir by $\Delta$T 
D) Lower the temperature of the cold reservoir by $\Delta$T 
E) Lower the temperature of the hot reservoir by (1/2)$\Delta$T and raise the temperature of the cold reservoir by (1/2)$\Delta$T 
A) Raise the temperature of the hot reservoir by $\Delta$T 
B) Raise the temperature of the cold reservoir by $\Delta$T 
C) Lower the temperature of the hot reservoir by $\Delta$T 
D) Lower the temperature of the cold reservoir by $\Delta$T 
E) Lower the temperature of the hot reservoir by (1/2)$\Delta$T and raise the temperature of the cold reservoir by (1/2)$\Delta$T

Question 20

The difference in entropy $\Delta$S = SB - SA for two states A and B of a system can computed as the integral $\int$dQ/T provided:

Accepted Answer

A) A and B are on the same adiabat 
B) A and B have the same temperature 
C) a reversible path is used for the integral 
D) the change in internal energy is first computed 
E) the energy absorbed as heat by the system is first computed 
A) A and B are on the same adiabat 
B) A and B have the same temperature 
C) a reversible path is used for the integral 
D) the change in internal energy is first computed 
E) the energy absorbed as heat by the system is first computed

Exam 20: Entropy and the Second Law of Thermodynamics

On a warm day a pool of water transfers energy to the air as heat and freezes.This is a direct violation of:

A force of 5 N stretches an elastic band at room temperature.The rate at which its entropy changes as it stretches is about:

An ideal gas is to taken reversibly from state i, at temperature T1, to other states labeled I, II, III, IV and V on the p-V diagram below.All are at the same temperature T2. Rank the five processes according to the change in entropy of the gas, least to greatest.

A Carnot heat engine runs between a cold reservoir at temperature TL and a hot reservoir at temperature TH.You want to increase its efficiency.Of the following, which change results in the greatest increase in efficiency? The value of Δ\DeltaΔ T is the same for all changes.

Possible units of entropy are:

For a system of molecules,

An ideal gas, consisting of n moles, undergoes a reversible isothermal process during which the volume changes from Vi to Vf.The change in entropy of the thermal reservoir in contact with the gas is given by:

A heat engine in each cycle absorbs energy from a reservoir as heat and does an equivalent amount of work, with no other changes.This engine violates:

An inventor claims to have a heat engine that has efficiency of 40% when it operates between a high temperature reservoir of 150 °\degree° C and a low temperature reservoir of 30 °\degree° C.This engine:

In a reversible process the system:

For all irreversible processes involving a system and its environment:

According to the second law of thermodynamics:

Let k be the Boltzmann constant.If the configuration of the molecules in a gas changes so that the multiplicity is reduced to one-third its previous value, the entropy of the gas changes by:

Which of the following is NOT a state variable?

A Carnot cycle heat engine operates between 400 K and 500 K.Its efficiency is:

Consider all possible isothermal contractions of an ideal gas.The entropy of the gas:

A Carnot refrigerator runs between a cold reservoir at temperature TL and a hot reservoir at temperature TH.You want to increase its coefficient of performance.Of the following, which change results in the greatest increase in the coefficient? The value of Δ\DeltaΔ T is the same for all changes.

The difference in entropy Δ\DeltaΔ S = SB - SA for two states A and B of a system can computed as the integral ∫\int∫ dQ/T provided:

Measurement

Motion Along a Straight Line

Vector

Motion in Two and Three Dimensions

Force and Motion I

Force and Motion II

Kinetic Energy and Work

Potential Energy and Conservation of Energy

Center of Mass and Linear Momentum

Rotation

Rolling, Torque, and Angular Momentum

Equilibrium and Elasticity

Gravitation

Fluids

Oscillations

Waves I

Waves II

Temperature, Heat, and the First Law of Thermodynamics

The Kinetic Theory of Gases

Electric Charge

Electric Fields

Gauss Law

Electric Potential

Capacitance

Current and Resistance

Circuits

Magnetic Fields

Magnetic Fields Due to Currents

Induction and Inductance

Electromagnetic Oscillations and Alternating Current

Maxwells Equations; Magnetism of Matter

Electromagnetic Waves

Images

Interference

Diffraction

Relativity

Photons and Matter Waves

More About Matter Waves

All About Atoms

Conduction of Electricity in Solids

Nuclear Physics

Energy From the Nucleus

Quarks, Leptons, and the Big Bang

Filters

An ideal gas is to taken reversibly from state i, at temperature T₁, to other states labeled I, II, III, IV and V on the p-V diagram below.All are at the same temperature T_2. Rank the five processes according to the change in entropy of the gas, least to greatest.

A Carnot heat engine runs between a cold reservoir at temperature T_L and a hot reservoir at temperature T_H.You want to increase its efficiency.Of the following, which change results in the greatest increase in efficiency? The value of $\Delta$ T is the same for all changes.

An ideal gas, consisting of n moles, undergoes a reversible isothermal process during which the volume changes from V_i to V_f.The change in entropy of the thermal reservoir in contact with the gas is given by:

An inventor claims to have a heat engine that has efficiency of 40% when it operates between a high temperature reservoir of 150 $\degree$ C and a low temperature reservoir of 30 $\degree$ C.This engine:

A Carnot refrigerator runs between a cold reservoir at temperature T_L and a hot reservoir at temperature T_H.You want to increase its coefficient of performance.Of the following, which change results in the greatest increase in the coefficient? The value of $\Delta$ T is the same for all changes.

The difference in entropy $\Delta$ S = S_B - S_A for two states A and B of a system can computed as the integral $\int$ dQ/T provided: