Question 1

A storage area,which is maintained at 22 $\degree$C,has an outside wall of area  .On a day when the outside temperature is 8.0 $\degree$C,the rate of energy transfer through the wall is 220 W.What is the R-value of the wall?
A) 
B) 
C) 
D)

Accepted Answer

The answer of A storage area,which is maintained at 22...

Question 2

Carbon dioxide and water molecules in the atmosphere will absorb:
A)infrared light.
B)visible light.
C)ultraviolet light.
D)radio waves.

Accepted Answer

Carbon dioxide and water molecules in the atmosphere are known as greenhouse gases, and they absorb infrared radiation from the Earth's surface and re-radiate it back to the surface, causing the greenhouse effect. Therefore, they absorb infrared light.

Question 3

A person is losing thermal energy through the skin at a rate of 120 W when his skin temperature is 30 $\degree$C.He puts on a sweater,and his skin temperature rises to 33 $\degree$C.The effective thermal conductivity between his core and the environment changes from 0.22 W/m·K to 0.18 W/m·K.At what rate is he now losing thermal energy?
A)98 W
B)69 W
C)63 W
D)56 W

Accepted Answer

The answer of A person is losing thermal energy through...

Question 4

A metal bar is used to conduct heat.When the temperature at one end is 100 $\degree$C and at the other is 20 $\degree$C,heat is transferred at a rate of 16 J/s.The bar is then stretched uniformly to twice its original length.If again it has ends at 100 $\degree$C and 20 $\degree$C,at what rate will heat be transferred between it ends?
A)4 J/s
B)8 J/s
C)16 J/s
D)32 J/s

Accepted Answer

When the bar is stretched to twice its original length, its cross-sectional area decreases, which affects the rate of heat transfer. The rate of heat transfer is inversely proportional to the length of the bar and directly proportional to the cross-sectional area. Since the length is doubled and the area is halved, the rate of heat transfer becomes one-fourth of the original rate, which is 4 J/s.

Question 5

What temperature increase is necessary to increase the power radiated from an object by a factor of 8?
A)8 K
B)2 K
C)100%
D)about 68%

Accepted Answer

The power radiated by an object is proportional to the fourth power of its temperature (Stefan-Boltzmann Law). To increase the power by a factor of 8, the temperature must increase by the fourth root of 8, which is approximately 1.68, or about 68%.

Question 6

The tungsten filament of a light bulb has an operating temperature of about 2 100 K.If the emitting area of the filament is 1.0 cm²,and its emissivity is 0.68,what is the power output of the light bulb? (s = 5.67 ´ 10^-8 W/m²*K⁴) A)100 W B)75 W C)60 W D)40 W

Accepted Answer

The answer of The tungsten filament of a light bulb...

Question 7

I place a 500-g ice cube (initially at 0 $\degree$C)in a Styrofoam box with wall thickness 1.0 cm and total surface area 600 cm².If the air surrounding the box is at 20 $\degree$C and after 4 hours the ice is completely melted,what is the conductivity of the Styrofoam material? (L_f = 80 cal/g) A)9.6 x 10^-5 cal/s*cm* $\degree$C B)2.8 x 10^-6 cal/s*cm* $\degree$C C)1.15 x 10^-2 cal/s*cm* $\degree$C D)2.3 x 10^-4 cal/s*cm* $\degree$C

Accepted Answer

The answer of I place a 500-g ice cube (initially...

Question 8

In winter,light-colored clothes will keep you warmer than dark-colored clothes if:
A)you are warmer than your surroundings.
B)you are at the same temperature as your surroundings.
C)you are cooler than your surroundings.
D)you are standing in sunlight.

Accepted Answer

The answer of In winter,light-colored clothes will keep you warmer...

Question 9

A metal bar is used to conduct heat.When the temperature at one end is 100 $\degree$C and at the other is 20 $\degree$C,heat is transferred at a rate of 16 J/s.If the temperature of the hotter end is reduced to 80 $\degree$C,what will be the rate of heat transfer?
A)4 J/s
B)8 J/s
C)9 J/s
D)12 J/s

Accepted Answer

We can use the formula for heat transfer through a metal bar:

Q/t = kA(delta T)/L

Where Q/t is the rate of heat transfer, k is the thermal conductivity of the metal, A is the cross-sectional area of the bar, delta T is the temperature difference between the two ends, and L is the length of the bar.

Since k, A, and L are constant, we can set up a proportion:

(Q/t)1/(Q/t)2 = (delta T)1/(delta T)2

where 1 represents the initial conditions and 2 represents the new conditions.

Plugging in the initial values, we have:

16/t = kA(100 - 20)/L

Simplifying, we get:

t = kAL/16(80 - 20)

Plugging in the new temperature and solving for the new rate of heat transfer:

Q/t = kA(80 - 20)/L

Q/t = 3/4(16 J/s)

Q/t = 12 J/s

Therefore, the answer is (D) 12 J/s.

Question 10

In order to conserve energy,it is decided to increase the R-value of an outside wall from  by adding an inexpensive layer of sheathing on the inside of the wall which has an R-value of  .When the temperature difference between the inside and outside is 20 $\degree$C,by what percentage is the rate of energy transfer through the wall reduced by this added insulation?
A)37%
B)58%
C)63%
D)This cannot be found without also knowing the area of the wall.

Accepted Answer

The answer of In order to conserve energy,it is decided...

Question 11

A person has a thermal conductivity of 0.18 W/m·K between his inner core and his skin with an effective shell thickness of 1.8 cm between his core and skin.If his inner core is at the normal 98.6 $\degree$F,and his skin has a surface area of 1.64  ,what will be his rate of loss of thermal energy due to conduction through his skin if his skin temperature is 31.0 $\degree$?
A)65 W
B)52 W
C)89 W
D)98 W

Accepted Answer

The answer of A person has a thermal conductivity of...

Question 12

Which of the following produces greenhouse gases?
A)burning fossil fuel
B)digestive processes in cows
C)automobile pollution
D)all of the above

Accepted Answer

All of the choices listed produce greenhouse gases. Burning fossil fuels releases carbon dioxide into the atmosphere, cow digestive processes release methane, and automobile pollution releases a variety of greenhouse gases such as carbon dioxide, methane, and nitrous oxide.

Question 13

In a greenhouse,electromagnetic energy in the form of visible light enters the glass panes and is absorbed and then reradiated.What happens to this reradiated electromagnetic radiation from within the greenhouse?
A)100% returns to the atmosphere.
B)It's partially blocked by glass.
C)It's transformed into ultraviolet upon striking the glass.
D)It's reflected as visible light upon striking the glass.

Accepted Answer

The reradiated electromagnetic radiation from within the greenhouse is partially blocked by glass, as some of it is reflected back into the greenhouse and some escapes through the glass into the atmosphere. This is what creates the greenhouse effect, where the trapped radiation heats up the greenhouse.

Question 14

Of the planets with atmospheres,which is the warmest?
A)Venus
B)Earth
C)Mars
D)Jupiter

Accepted Answer

Venus is the warmest planet with an average surface temperature of 460°C due to its thick greenhouse gas atmosphere, trapping heat from the sun. Earth has a cooler average surface temperature of 15°C due to its thinner atmosphere and distance from the sun. Mars has a very thin atmosphere and cold surface temperatures, averaging -63°C. Jupiter is a gas giant with no solid surface to have a surface temperature.

Question 15

Which type of heating causes sunburn?
A)conduction
B)convection
C)radiation
D)all of the above

Accepted Answer

Radiation is the type of heating that causes sunburn. Both conduction and convection require physical contact or movement of heat through a substance, while radiation is the transfer of energy through electromagnetic waves. The sun emits ultraviolet radiation which can cause damage to the skin and result in sunburn.

Question 16

At high noon,the sun delivers 1 000 W to each square meter of a blacktop road.What is the equilibrium temperature of the hot asphalt,assuming its emissivity e = 1? (s = 5.67 x10^-8 W/m²*K⁴). A)75 $\degree$C B)84 $\degree$C C)91 $\degree$C D)99 $\degree$C

Accepted Answer

The equilibrium temperature can be calculated using the Stefan-Boltzmann law: 
P = σεAT^4 
where P is the power received by the surface, σ is the Stefan-Boltzmann constant, A is the surface area, ε is the emissivity, and T is the temperature in Kelvin. 
Rearranging for T, we get: 
T = (P/σεA)^1/4 
Substituting the known values, we get: 
T = [(1000 W/m^2) / (5.67 x 10^-8 W/m^2K^4)(1)(1 m^2)]^1/4 
T = 90.7 K 
Converting to Celsius: 
T = 90.7 ºC ≈ 91 ºC 
Therefore, the best choice is C.

Question 17

An object at 27 $\degree$C has its temperature increased to 37 $\degree$C.The power then radiated by this object increases by how many percent?
A)3.3
B)14
C)37
D)253

Accepted Answer

The power radiated by an object is given by the Stefan-Boltzmann law, which states that P = σAT⁴, where P is the power, A is the surface area, T is the absolute temperature, and σ is the Stefan-Boltzmann constant.

Assuming that the surface area and emissivity of the object remain constant, we can calculate the percent increase in power as follows:

Let P1 be the initial power and P2 be the final power. Then:

P1 = σA(27+273)^4 = σA(300)^4
P2 = σA(37+273)^4 = σA(310)^4

The percent increase in power is:

(P2 - P1)/P1 x 100% = (σA(310)^4 - σA(300)^4)/(σA(300)^4) x 100%
= (310/300)^4 - 1 x 100% = 14.4%

Therefore, the answer is (B) 14.

Question 18

The surface of the Sun has a temperature of about 5 800 K.If the radius of the Sun is 7 x 10⁸ m,determine the power output of the sun.(Take e = 1,and s = 5.67 x 10^-8 W/m²*K⁴). A)3.95 x 10²⁶ W B)5.17 x 10²⁷ W C)9.62 x 10²⁸ W D)6.96 x 10³⁰ W

Accepted Answer

The power output of the Sun can be calculated using the Stefan-Boltzmann law: P = σeA(T^4). Here, σ = 5.67 x 10^-8 W/m^2K^4, e = 1, A = 4πr^2 (surface area of the Sun), and T = 5800 K. Substituting the values, P = 5.67 x 10^-8 * 4π * (7 x 10^8)^2 * (5800)^4 ≈ 3.95 x 10^26 W.

Question 19

A silver bar of length 30 cm and cross-sectional area 1.0 cm² is used to transfer heat from a 100*C reservoir to a 0 $\degree$C block of ice.How much ice is melted per second? (For silver,k = 427 J/s*m* $\degree$C.For ice,L_f = 334 000 J/kg. ) A)4.2 g/s B)2.1 g/s C)0.80 g/s D)0.043 g/s

Accepted Answer

The answer of A silver bar of length 30 cm...

Question 20

Consider two different rods.The greatest thermal conductivity will be in the rod with:
A)electrons that are freer to move from atom to atom.
B)the greater specific heat.
C)the greater cross-sectional area.
D)the greater length.

Accepted Answer

Thermal conductivity is dependent on the movement of electrons from atom to atom, so the rod with electrons that are freer to move will have the greater thermal conductivity. Specific heat, cross-sectional area, and length do not directly affect thermal conductivity.

Quiz 11: Energy in Thermal Processes

Carbon dioxide and water molecules in the atmosphere will absorb:

What temperature increase is necessary to increase the power radiated from an object by a factor of 8?

The tungsten filament of a light bulb has an operating temperature of about 2 100 K.If the emitting area of the filament is 1.0 cm²,and its emissivity is 0.68,what is the power output of the light bulb? (s = 5.67 ´ 10^-8 W/m²*K⁴)

I place a 500-g ice cube (initially at 0 $\degree$ C) in a Styrofoam box with wall thickness 1.0 cm and total surface area 600 cm².If the air surrounding the box is at 20 $\degree$ C and after 4 hours the ice is completely melted,what is the conductivity of the Styrofoam material? (L_f = 80 cal/g)

In winter,light-colored clothes will keep you warmer than dark-colored clothes if:

A metal bar is used to conduct heat.When the temperature at one end is 100 $\degree$ C and at the other is 20 $\degree$ C,heat is transferred at a rate of 16 J/s.If the temperature of the hotter end is reduced to 80 $\degree$ C,what will be the rate of heat transfer?

Which of the following produces greenhouse gases?

In a greenhouse,electromagnetic energy in the form of visible light enters the glass panes and is absorbed and then reradiated.What happens to this reradiated electromagnetic radiation from within the greenhouse?

Of the planets with atmospheres,which is the warmest?

Which type of heating causes sunburn?

At high noon,the sun delivers 1 000 W to each square meter of a blacktop road.What is the equilibrium temperature of the hot asphalt,assuming its emissivity e = 1? (s = 5.67 x10^-8 W/m²*K⁴) .

An object at 27 $\degree$ C has its temperature increased to 37 $\degree$ C.The power then radiated by this object increases by how many percent?

The surface of the Sun has a temperature of about 5 800 K.If the radius of the Sun is 7 x 10⁸ m,determine the power output of the sun.(Take e = 1,and s = 5.67 x 10^-8 W/m²*K⁴) .

A silver bar of length 30 cm and cross-sectional area 1.0 cm² is used to transfer heat from a 100C reservoir to a 0 $\degree$ C block of ice.How much ice is melted per second? (For silver,k = 427 J/sm* $\degree$ C.For ice,L_f = 334 000 J/kg. )

Consider two different rods.The greatest thermal conductivity will be in the rod with:

Quiz 11: Energy in Thermal Processes

A storage area,which is maintained at 22 °\degree° C,has an outside wall of area .On a day when the outside temperature is 8.0 °\degree° C,the rate of energy transfer through the wall is 220 W.What is the R-value of the wall?