Question 1

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)

Accepted Answer

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

Question 2

Inside a house, stepping on a tile floor barefooted may feel almost cold, but stepping on carpet in an adjacent room feels comfortably warm.Why is this?

Accepted Answer

The thermal conductivity of carpet is less than that of tile, meaning that carpet is a better insulator and does not easily transfer heat from the room or the foot. Therefore, it feels warmer to the touch than the tile.

Question 3

Which type of heating causes sunburn?

Accepted Answer

Sunburn is caused by exposure to ultraviolet radiation from the sun.

Question 4

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

Accepted Answer

Thermal conductivity is related to the ability of electrons to move from atom to atom. The more freely they can move, the better the thermal conductivity. Therefore, the rod with electrons that are freer to move from atom to atom will have the greatest thermal conductivity.

Question 5

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?

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 6

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

Accepted Answer

The answer of The surface of the Sun has a...

Question 7

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?

Accepted Answer

According to the Stefan-Boltzmann law, the power (P) radiated by an object is proportional to the fourth power of its absolute temperature (T): P ∝ T^4. Therefore, if the temperature increases from T1 to T2, the power increases by (T2/T1)^4. In this case, the initial and final temperatures are 27+273=300K and 37+273=310K, respectively. So the power increases by (310/300)^4 = 1.139, or 13.9% (rounded to the nearest whole number), which is closest to choice B (14).

Question 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)

Accepted Answer

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

Question 9

Pennies used to be made of copper, but now they are made of copper-coated zinc.If one were to do a precise calorimetry experiment to determine the specific heat of the new pennies, what would the result be?

Accepted Answer

Since the specific heat of a material depends on its composition, a precise calorimetry experiment would reveal that the specific heat of the copper-coated zinc penny is between that of copper and that of zinc. The specific heat would depend on the thickness of the copper coating, as this would determine the amount of copper contributing to the overall specific heat of the penny.

Question 10

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?

Accepted Answer

The reradiated electromagnetic radiation from within the greenhouse is partially blocked by glass. Glass panes absorb some of this radiation and reradiate it back into the greenhouse, while also reflecting some of it back towards the atmosphere. This is why greenhouses stay warmer than the surrounding environment, as the glass acts as a barrier to prevent heat from escaping.

Question 11

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

Accepted Answer

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

Question 12

A silver bar of length 30 cm and cross-sectional area 1.0 cm² is used to transfer heat from a 100$\degree$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.)

Accepted Answer

We need to use the formula for heat transfer through a bar: Q = kAΔT/Δx, where Q is the rate of heat transfer, k is the thermal conductivity, A is the cross-sectional area, ΔT is the temperature difference, and Δx is the length of the bar. Using the given values, we get: Q = (427 J/s*m*°C)(1.0 cm^2)(100°C - 0°C)/(0.30 m) = 42700 J/s This is the rate of heat delivered to the ice. To find the rate of melting, we need to divide by the heat of fusion of ice: melting rate = Q/L_f = (42700 J/s)/(334000 J/kg) = 0.128 g/s, which is equivalent to 0.043 g/s when rounded to two significant figures. Therefore, the answer is D.

Question 13

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

Accepted Answer

The answer of What temperature increase is necessary to increase...

Question 14

Of the planets with atmospheres, which is the warmest?

Accepted Answer

Venus is the warmest planet with an average surface temperature of about 462 °C (864 °F) due to its thick atmosphere which traps heat.

Question 15

Which of the following produces greenhouse gases?

Accepted Answer

All of the choices listed produce greenhouse gases. Burning fossil fuels releases carbon dioxide, methane, and other gases. Digestive processes in cows and other livestock produce methane, and automobile pollution includes carbon dioxide and other greenhouse gases.

Question 16

The inside of a house is at 20$\degree$C on an early morning when the temperature outside is 15$\degree$C.The next morning the inside temperature is the same but the outside temperature is now 10$\degree$C.How much does the energy per unit time lost by conduction through the walls, windows, doors, etc., change for the house from the first morning to the second one?

Accepted Answer

The answer of The inside of a house is at...

Question 17

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 * 10^-8 W/m²*K⁴) .

Accepted Answer

The equilibrium temperature of the hot asphalt can be found using the Stefan-Boltzmann law:

P = εσAT^4

Where P is the power absorbed by the asphalt per unit area (1000 W/m^2), ε is the emissivity (1 in this case), σ is the Stefan-Boltzmann constant (5.67 x 10^-8 W/m^2K^4), A is the surface area of the asphalt, and T is the equilibrium temperature we want to find.

We can solve for T:

T^4 = P/(εσA)
T^4 = (1000 W/m^2)/(1 x 5.67 x 10^-8 W/m^2K^4 x A)

The surface area of the asphalt is not specified, so we can assume a standard value of 1 m^2 for simplicity:

T^4 = (1000 W/m^2)/(1 x 5.67 x 10^-8 W/m^2K^4 x 1 m^2) = 3.53 x 10^9 K^4
T = (3.53 x 10^9 K^4)^(1/4) = 91°C

Converting to Fahrenheit, we get:

T = 91°C x 1.8 + 32 = 195.8°F

Rounding to the nearest whole number, we get 196°F, which is closest to answer choice C (91°C or 195.8°F).

Question 18

Carbon dioxide and water molecules in the atmosphere will absorb:

Accepted Answer

Carbon dioxide and water molecules in the atmosphere are known greenhouse gases that absorb and re-emit long-wave, infrared radiation, which leads to the heating of the atmosphere.

Question 19

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?

Accepted Answer

The answer of A metal bar is used to conduct...

Question 20

Two stars, A and B, have the same emissivity, but the radii and surface temperatures are different with R_A = 0.5 R_B, and T_A = 2 T_B.Assuming the temperature of space to be negligible, which star radiates the most energy per unit time?

Accepted Answer

The energy radiated per unit time by a star can be calculated using the Stefan-Boltzmann law, which states that the power radiated per unit area of a black body is proportional to the fourth power of its temperature (P = σAT^4, where σ is the Stefan-Boltzmann constant, A is the surface area, and T is the temperature). Given that Star A has twice the temperature of Star B (T_A = 2T_B), its radiated power per unit area will be 2^4 = 16 times greater. Although Star A has half the radius of Star B (R_A = 0.5R_B), its surface area (A = 4πR^2) will be 0.5^2 = 0.25 times that of Star B. Therefore, the total power radiated by Star A will be 16 * 0.25 = 4 times that of Star B, making Star A the star that radiates the most energy per unit time.

Quiz 11: Energy in Thermal Processes

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)

Inside a house, stepping on a tile floor barefooted may feel almost cold, but stepping on carpet in an adjacent room feels comfortably warm.Why is this?

Which type of heating causes sunburn?

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

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?

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

Pennies used to be made of copper, but now they are made of copper-coated zinc.If one were to do a precise calorimetry experiment to determine the specific heat of the new pennies, what would the result be?

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?

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

A silver bar of length 30 cm and cross-sectional area 1.0 cm² is used to transfer heat from a 100 $\degree$ C 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.)

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

Of the planets with atmospheres, which is the warmest?

Which of the following produces greenhouse gases?

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 * 10^-8 W/m²*K⁴) .

Carbon dioxide and water molecules in the atmosphere will absorb:

Two stars, A and B, have the same emissivity, but the radii and surface temperatures are different with R_A = 0.5 R_B, and T_A = 2 T_B.Assuming the temperature of space to be negligible, which star radiates the most energy per unit time?

Quiz 11: Energy in Thermal Processes

Inside a house, stepping on a tile floor barefooted may feel almost cold, but stepping on carpet in an adjacent room feels comfortably warm.Why is this?

Which type of heating causes sunburn?

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

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?

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

Pennies used to be made of copper, but now they are made of copper-coated zinc.If one were to do a precise calorimetry experiment to determine the specific heat of the new pennies, what would the result be?

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?

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

A silver bar of length 30 cm and cross-sectional area 1.0 cm2 is used to transfer heat from a 100 °\degree° 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, Lf = 334 000 J/kg.)

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

Of the planets with atmospheres, which is the warmest?

Which of the following produces greenhouse gases?

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 * 10-8 W/m2*K4) .

Carbon dioxide and water molecules in the atmosphere will absorb:

Two stars, A and B, have the same emissivity, but the radii and surface temperatures are different with RA = 0.5 RB, and TA = 2 TB.Assuming the temperature of space to be negligible, which star radiates the most energy per unit time?

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?

The surface of the Sun has a temperature of about 5 800 K.If the radius of the Sun is 7 * 10⁸ m, determine the power output of the sun.(Take e = 1, and s = 5.67 * 10^-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 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 silver bar of length 30 cm and cross-sectional area 1.0 cm² is used to transfer heat from a 100 $\degree$ C 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.)

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 * 10^-8 W/m²*K⁴) .

Two stars, A and B, have the same emissivity, but the radii and surface temperatures are different with R_A = 0.5 R_B, and T_A = 2 T_B.Assuming the temperature of space to be negligible, which star radiates the most energy per unit time?