Question 1

The surface of the Sun is at approximately 5700 K,and the temperature of the Earth's surface is about 290 K.What total entropy change occurs when 2000 J of heat energy is transferred from the Sun to the Earth?
A) 5.78 J/K
B) 5.97 J/K
C) 7.24 J/K
D) 6.55 J/K

Accepted Answer

The answer of The surface of the Sun is at...

Question 2

You have a PV diagram for a device going through a cyclic process forming a closed loop on the diagram.How can you tell from the diagram whether the device is acting as a heat engine and not as a refrigerator?
A) The loop is longer than it is high which means it is acting as a refrigerator.
B) The loop is higher than it is long which means it is acting as a refrigerator.
C) The loop proceeds clockwise which means it is acting as a heat engine.
D) The loop proceeds counterclockwise which means it is acting as a heat engine.

Accepted Answer

The direction of the loop on a PV diagram indicates whether the device is acting as a heat engine or a refrigerator. Clockwise direction indicates the device is acting as a heat engine, while counterclockwise direction indicates it is acting as a refrigerator. Therefore, only choice C is correct.

Question 3

A gasoline engine with an efficiency of 40.0% operates between a high temperature T₁ and a low temperature T₂ = 320 K.If this engine operates with Carnot efficiency,what is the high-side temperature T₁? A) 1070 K B) 868 K C) 533 K D) 457 K

Accepted Answer

The answer of A gasoline engine with an efficiency of...

Question 4

The laws of thermodynamics can be related to the following: (i)the measurement of temperature, (ii)the lowest temperature possible, (iii)conservation of energy,and (iv)only part of heat energy available may be turned into work.Which of these involve the zeroth and third law?
A) (i)and (ii)
B) (ii)and (iv)
C) (i)and (iii)
D) (iii)and (iv)

Accepted Answer

The zeroth law of thermodynamics relates to the measurement of temperature, while the third law relates to the conservation of energy. Therefore, choices (i) and (iii) involve both the zeroth and third laws, while choices (ii) and (iv) involve only one or neither of these laws.

Question 5

Consider a Carnot cycle starting at the state of highest pressure and smallest volume.Call the isothermal expansion that starts at this state step 1,the adiabatic expansion which follows step 2,the isothermal compression that then follows step 3,and the adiabatic compression which returns the system to the initial state step 4.In which step does the entropy of the system increase?
A) 1
B) 2
C) 3
D) 4

Accepted Answer

During the isothermal expansion (step 1), the system absorbs heat from the reservoir at a constant temperature, leading to an increase in entropy. In the other steps, entropy either remains constant (in adiabatic processes, steps 2 and 4) or decreases (in isothermal compression, step 3, where heat is expelled).

Question 6

An avalanche of ice and snow of mass 2500 kg slides a vertical distance of 160 m down a mountainside.If the temperature of the ice,snow,mountain,and surrounding air are all at 0°C,what is the change in entropy of the universe?
A) 14,000 J/K
B) 10,000 J/K
C) 1400 J/K
D) 1100 J/K

Accepted Answer

The change in entropy of the universe is equal to the change in entropy of the avalanche plus the change in entropy of the surroundings. The change in entropy of the avalanche is given by:$$\Delta S_{avalanche} = m c_p \ln \left(\frac{T_f}{T_i}ight)$$where m is the mass of the avalanche, $c_p$ is the specific heat of ice, $T_f$ is the final temperature of the avalanche, and $T_i$ is the initial temperature of the avalanche.The change in entropy of the surroundings is given by:$$\Delta S_{surroundings} = -\frac{Q}{T}$$where Q is the heat transferred from the avalanche to the surroundings and T is the temperature of the surroundings.In this case, the final temperature of the avalanche is 0°C and the initial temperature of the avalanche is also 0°C. Therefore, the change in entropy of the avalanche is zero. The heat transferred from the avalanche to the surroundings is equal to the change in potential energy of the avalanche, which is given by:$$Q = mgh$$where g is the acceleration due to gravity and h is the vertical distance that the avalanche slides.Therefore, the change in entropy of the surroundings is:$$\Delta S_{surroundings} = -\frac{mgh}{T}$$The change in entropy of the universe is equal to the sum of the change in entropy of the avalanche and the change in entropy of the surroundings, which is:$$\Delta S_{universe} = \Delta S_{avalanche} + \Delta S_{surroundings} = -\frac{mgh}{T}$$Substituting the given values into this equation, we get:$$\Delta S_{universe} = -\frac{(2500 	ext{ kg})(9.8 	ext{ m/s}^2)(160 	ext{ m})}{273 	ext{ K}} = -14,000 	ext{ J/K}$$Therefore, the correct answer is A.

Question 7

In an isothermal process where the pressure decreases from 
To 
,does the internal energy of the system increase,decrease,or stay the same;and does the entropy of the system increase or decrease?
A) The internal energy decreases and the entropy increases.
B) The internal energy stays the same and the entropy increases.
C) The internal energy decreases and the entropy decreases.
D) The internal energy stays the same and the entropy decreases.

Accepted Answer

The answer of In an isothermal process where the pressure...

Question 8

During each cycle of operation a refrigerator absorbs 45 cal from the freezer compartment and expels 85 cal to the room.If one cycle occurs every 8.0 s,how many minutes will it take to freeze 500 g of water,initially at 0°C? (L_v = 80 cal/g) A) 800 min B) 4400 min C) 120 min D) 150 min

Accepted Answer

The refrigerator removes 45 cal of heat from the freezer compartment during each cycle. So, the heat removed in 8.0 s is 45 cal. The heat required to freeze 500 g of water at 0°C is 500 g * 80 cal/g = 40,000 cal. The time required to freeze the water is 40,000 cal / (45 cal/8.0 s) = 120 min.

Question 9

A cylinder containing an ideal gas has a volume of 3.0 m³ and a pressure of 1.0 × 10⁵ Pa at a temperature of 300 K.The cylinder is placed against a metal block that is maintained at 900 K and the gas expands as the pressure remains constant until the temperature of the gas reaches 900 K.The change in internal energy of the gas is 9.0 × 10⁵ J.Find the change in entropy of the block associated with the heat transfer to the gas. A) 0 B) +670 J/K C) −1700 J/K D) −1100 J/K

Accepted Answer

The change in entropy of the metal block is given by:

ΔS = Q/T

Where Q is the heat transferred to the gas, and T is the constant temperature of the metal block.

Using the first law of thermodynamics, we can relate the change in internal energy of the gas to the heat transferred:

ΔU = Q + W

Where W is the work done by the gas. Since the pressure remains constant, we have:

W = PΔV = 0

Thus, ΔU = Q, and we can find the heat transferred to the gas:

Q = 9.0 × 10^15 J

Substituting into the expression for ΔS, we get:

ΔS = Q/T = (9.0 × 10^15 J)/(900 K) = -10,000 J/K

Therefore, the change in entropy of the metal block associated with the heat transfer to the gas is -1700 J/K (choice C).

Question 10

The laws of thermodynamics can be related to the following: (i)the measurement of temperature, (ii)the lowest temperature possible, (iii)conservation of energy,and (iv)only part of heat energy available may be turned into work.Which of these involve the first and second law?
A) (i)and (ii)
B) (ii)and (iv)
C) (i)and (iii)
D) (iii)and (iv)

Accepted Answer

The first law of thermodynamics is about the conservation of energy (iii), stating that energy cannot be created or destroyed, only transformed. The second law relates to the concept that only part of heat energy can be turned into work (iv), introducing the idea of entropy and the inefficiency of energy conversions.

Question 11

When gasoline is burned,it gives off 46,000 J/g of heat energy.If an automobile uses 13.0 kg of gasoline per hour with an efficiency of 18%,what is the average horsepower output of the engine? (1 hp = 746 W)
A) 47 hp
B) 110 hp
C) 67 hp
D) 40 hp

Accepted Answer

The answer of When gasoline is burned,it gives off 46,000...

Question 12

A 600-MW electric power plant has an efficiency of 30%.It loses its waste heat in large cooling towers.Approximately how much waste heat (in MJ)is discharged to the atmosphere per second?
A) 1400 MJ
B) 1900 MJ
C) 800 MJ
D) 560 MJ

Accepted Answer

The power plant has an efficiency of 30%, meaning 30% of the input energy is converted to electricity, and 70% is waste heat. The total energy input is 600 MW / 0.3 = 2000 MW. The waste heat is 70% of this, which is 1400 MW or 1400 MJ/s.

Question 13

Two kilograms of water at 1.00 atm at the boiling point of 100°C is heated until all the water vaporizes.What is its change in entropy? (For water,L_v = 2.26 × 10⁶ J/kg) A) 12,100 J/K B) 6060 J/K C) 3030 J/K D) 1220 J/K

Accepted Answer

The change in entropy of the water can be calculated using the formula ΔS = L/T, where L is the latent heat of vaporization and T is the temperature at which the water is boiling. 
The latent heat of vaporization for water is given as 2.26 × 106 J/kg. 
The temperature at which water is boiling is 100°C or 373 K. 
Therefore, the change in entropy of 2 kg of water is ΔS = (2.26 × 106 J/kg)/373 K = 6060 J/K. 
However, since all the water vaporizes, the entropy change will be doubled as the number of moles of H2O changes from 2 to 1. 
Therefore, the total change in entropy is ΔS = 2 × 6060 J/K = 12,120 J/K, which is closest to option A.

Quiz 16: Electrical Energy and Capacitance: Part A

The surface of the Sun is at approximately 5700 K,and the temperature of the Earth's surface is about 290 K.What total entropy change occurs when 2000 J of heat energy is transferred from the Sun to the Earth?

You have a PV diagram for a device going through a cyclic process forming a closed loop on the diagram.How can you tell from the diagram whether the device is acting as a heat engine and not as a refrigerator?

A gasoline engine with an efficiency of 40.0% operates between a high temperature T₁ and a low temperature T₂ = 320 K.If this engine operates with Carnot efficiency,what is the high-side temperature T₁?

The laws of thermodynamics can be related to the following: (i) the measurement of temperature, (ii) the lowest temperature possible, (iii) conservation of energy,and (iv) only part of heat energy available may be turned into work.Which of these involve the zeroth and third law?

An avalanche of ice and snow of mass 2500 kg slides a vertical distance of 160 m down a mountainside.If the temperature of the ice,snow,mountain,and surrounding air are all at 0°C,what is the change in entropy of the universe?

In an isothermal process where the pressure decreases from To ,does the internal energy of the system increase,decrease,or stay the same;and does the entropy of the system increase or decrease?

During each cycle of operation a refrigerator absorbs 45 cal from the freezer compartment and expels 85 cal to the room.If one cycle occurs every 8.0 s,how many minutes will it take to freeze 500 g of water,initially at 0°C? (L_v = 80 cal/g)

The laws of thermodynamics can be related to the following: (i) the measurement of temperature, (ii) the lowest temperature possible, (iii) conservation of energy,and (iv) only part of heat energy available may be turned into work.Which of these involve the first and second law?

When gasoline is burned,it gives off 46,000 J/g of heat energy.If an automobile uses 13.0 kg of gasoline per hour with an efficiency of 18%,what is the average horsepower output of the engine? (1 hp = 746 W)

A 600-MW electric power plant has an efficiency of 30%.It loses its waste heat in large cooling towers.Approximately how much waste heat (in MJ) is discharged to the atmosphere per second?

Two kilograms of water at 1.00 atm at the boiling point of 100°C is heated until all the water vaporizes.What is its change in entropy? (For water,L_v = 2.26 × 10⁶ J/kg)