Question 1

Which one of the following is not an example of convection?

Accepted Answer

A) Smoke rises above a fire. 
B) An eagle soars on an updraft of wind. 
C) A person gets a suntan on a beach. 
D) Spaghetti is cooked in water. 
E) An electric heater warms a room. 
A) Smoke rises above a fire. 
B) An eagle soars on an updraft of wind. 
C) A person gets a suntan on a beach. 
D) Spaghetti is cooked in water. 
E) An electric heater warms a room. C

Question 2

Which of the following materials is the best thermal conductor?

Accepted Answer

A) diamond 
B) Styrofoam 
C) nitrogen gas 
D) concrete 
E) goose down 
A) diamond 
B) Styrofoam 
C) nitrogen gas 
D) concrete 
E) goose down A

Question 3

At what rate is heat lost through a 1.5 m × 3.0 m rectangular glass windowpane that is 0.4 cm thick when the inside temperature is 22 °C and the outside temperature is 6.0 °C? The thermal conductivity for the glass is 0.75 W/(m · C°).

Accepted Answer

A) 560 W 
B) 1800 W 
C) 7200 W 
D) 3600 W 
E) 13 500 W 
A) 560 W 
B) 1800 W 
C) 7200 W 
D) 3600 W 
E) 13 500 W E

Question 4

Object A has an emissivity of 0.95; and its temperature is 25 °C.At what temperature (in degrees Celsius) does object B, whose emissivity is 0.50, emit radiation at the same rate as object A if both objects have the same surface area?

Accepted Answer

A) 29 °C 
B) 40 °C 
C) 61 °C 
D) 77 °C 
E) 93 °C 
A) 29 °C 
B) 40 °C 
C) 61 °C 
D) 77 °C 
E) 93 °C

Question 5

Which of the following materials is the poorest thermal conductor?

Accepted Answer

A) gold 
B) ice 
C) copper 
D) wood 
E) air 
A) gold 
B) ice 
C) copper 
D) wood 
E) air

Question 6

Heat is conducted by two cylindrical rods, one carbon and one aluminum, with identical cross-sectional area and length.The temperature difference between the ends of each rod is the same.Carbon has a thermal conductivity of 1100 J/(s . m .C°) and that of aluminum is 240 J/(s. m . C°).What percentage of the total energy transferred by the two rods each second is conducted by the silver rod?

Accepted Answer

A) 64 % 
B) 18 % 
C) 30 % 
D) 46 % 
E) 82 % 
A) 64 % 
B) 18 % 
C) 30 % 
D) 46 % 
E) 82 %

Question 7

Two bars, A and B, each of length 2.0 m and cross sectional area 1.0 mS1U1P12S1S1P0, are placed end to end as shown in the figure.   The thermal conductivities of the bars are
kS1U1B1AS1U1B0 = 439 J/(s . m. K) and kS1U1B1BS1U1B0 = 887 J/(s . m . K), respectively.The left end of bar A is maintained at 373 K while the right end of B is maintained at 273 K.
-What is the temperature at the interface between A and B?

Accepted Answer

A) 296 K 
B) 306 K 
C) 313 K 
D) 323 K 
E) 332 K 
A) 296 K 
B) 306 K 
C) 313 K 
D) 323 K 
E) 332 K

Question 8

Which one of the following graphs shows the rate at which heat is emitted from a hot body as a function of its Kelvin temperature T?

Accepted Answer

A) (a) 
B) (b) 
C) (c) 
D) (d) 
E) (e) 
A) (a) 
B) (b) 
C) (c) 
D) (d) 
E) (e)

Question 9

Suppose you are sitting next to a fire burning in a fireplace.One end of a metal poker has been left in the fire.Which one of the following statements concerning this situation is true?

Accepted Answer

A) You can feel the heat of the fire primarily because of convection. 
B) The end of the poker that is not in the fire is warmed through conduction. 
C) Heat escapes through the chimney primarily through conduction. 
D) You can feel the heat of the fire primarily because of conduction. 
E) The end of the poker that is not in the fire is warmed through convection. 
A) You can feel the heat of the fire primarily because of convection. 
B) The end of the poker that is not in the fire is warmed through conduction. 
C) Heat escapes through the chimney primarily through conduction. 
D) You can feel the heat of the fire primarily because of conduction. 
E) The end of the poker that is not in the fire is warmed through convection.

Question 10

Complete the following statement: The space between the inner walls of a thermos bottle is evacuated to minimize heat transfer by

Accepted Answer

A) radiation. 
B) conduction. 
C) conduction and convection. 
D) conduction and radiation. 
E) conduction, convection, and radiation. 
A) radiation. 
B) conduction. 
C) conduction and convection. 
D) conduction and radiation. 
E) conduction, convection, and radiation.

Question 11

A blue supergiant star has a radius of 7.4 × 1010 m.The spherical surface behaves as a blackbody radiator.If the surface temperature is 2.4 × 104 K, what is the rate at which energy is radiated from the star?

Accepted Answer

A) 1.2 × 103 J/s 
B) 9.4 × 1019 J/s 
C) 2.0 × 1023 J/s 
D) 8.2 × 1032 J/s 
E) 1.3 × 1033 J/s 
A) 1.2 × 103 J/s 
B) 9.4 × 1019 J/s 
C) 2.0 × 1023 J/s 
D) 8.2 × 1032 J/s 
E) 1.3 × 1033 J/s

Question 12

Two bars, A and B, each of length 2.0 m and cross sectional area 1.0 mS1U1P12S1S1P0, are placed end to end as shown in the figure.   The thermal conductivities of the bars are
kS1U1B1AS1U1B0 = 439 J/(s . m. K) and kS1U1B1BS1U1B0 = 887 J/(s . m . K), respectively.The left end of bar A is maintained at 373 K while the right end of B is maintained at 273 K.
-What is the rate of heat transfer through this combination?

Accepted Answer

A) 3.7 × 103 J/s 
B) 6.4 × 103 J/s 
C) 8.8 × 103 J/s 
D) 1.5 × 104 J/s 
E) 2.2 × 104 J/s 
A) 3.7 × 103 J/s 
B) 6.4 × 103 J/s 
C) 8.8 × 103 J/s 
D) 1.5 × 104 J/s 
E) 2.2 × 104 J/s

Question 13

On a cold winter day, the outside temperature is -5.0 °C while the interior of a well-insulated garage is maintained at 20.0 °C by an electric heater.Assume the walls have a total area of 75 m2, a thickness of 0.15 m, and a thermal conductivity of 0.042 W/(m · C°).What is the cost to heat the garage for six hours at these temperatures if the cost of electricity is $ 0.11/kWh? Note: 1 kWh = 3.6 × 106 J.

Accepted Answer

A) $ 0.18 
B) $ 0.44 
C) $ 0.61 
D) $ 0.35 
E) $ 1.09 
A) $ 0.18 
B) $ 0.44 
C) $ 0.61 
D) $ 0.35 
E) $ 1.09

Question 14

Complete the following statement: The interior of a thermos bottle is silvered to minimize heat transfer due to

Accepted Answer

A) radiation. 
B) conduction. 
C) conduction and convection. 
D) conduction and radiation. 
E) conduction, convection, and radiation. 
A) radiation. 
B) conduction. 
C) conduction and convection. 
D) conduction and radiation. 
E) conduction, convection, and radiation.

Question 15

Two cylindrical steel rods A and B have radii of 0.02 m and 0.04 m, respectively.The two steel rods conduct the same amount of heat per unit time for the same temperature differences between their two ends.What is the ratio of the lengths of the rods, LA/LB?

Accepted Answer

A) 0.25 
B) 0.50 
C) 1.00 
D) 2.00 
E) 4.00 
A) 0.25 
B) 0.50 
C) 1.00 
D) 2.00 
E) 4.00

Question 16

If a beaker of water is placed under a broiler so that the heating coil is above the beaker.It is observed that only the surface layer boils.The water at the bottom of the beaker remains close to the initial temperature of the water.Which of the following statements is the most reasonable conclusion to be drawn from these observations?

Accepted Answer

A) Water is a poor conductor of heat. 
B) The sample must contain impurities. 
C) Water is easily heated by radiation. 
D) Water exhibits anomalous thermal behavior. 
E) The molecular motion in the sample is not random. 
A) Water is a poor conductor of heat. 
B) The sample must contain impurities. 
C) Water is easily heated by radiation. 
D) Water exhibits anomalous thermal behavior. 
E) The molecular motion in the sample is not random.

Question 17

Two bars, A and B, each of length 2.0 m and cross sectional area 1.0 mS1U1P12S1S1P0, are placed end to end as shown in the figure.   The thermal conductivities of the bars are
kS1U1B1AS1U1B0 = 439 J/(s . m. K) and kS1U1B1BS1U1B0 = 887 J/(s . m . K), respectively.The left end of bar A is maintained at 373 K while the right end of B is maintained at 273 K.
-How much heat passes the interface between A and B in 6.0 s?

Accepted Answer

A) 6.0 × 104 J 
B) 1.5 × 103 J 
C) 1.2 × 105 J 
D) 8.8 × 104 J 
E) 3.0 × 104 J 
A) 6.0 × 104 J 
B) 1.5 × 103 J 
C) 1.2 × 105 J 
D) 8.8 × 104 J 
E) 3.0 × 104 J

Question 18

A beaker of water is placed on a Bunsen burner.As the lower layers of water are heated, they become less dense and rise.This permits cooler layers to move downward and be heated.Eventually, the water boils.Which method(s) of heat transfer is (are) primarily responsible for boiling the sample?

Accepted Answer

A) conduction 
B) convection 
C) radiation 
D) both conduction and radiation 
E) both conduction and convection 
A) conduction 
B) convection 
C) radiation 
D) both conduction and radiation 
E) both conduction and convection

Question 19

Complete the following statement: Most of the heat that is lost to space from the earth occurs by

Accepted Answer

A) conduction. 
B) convection. 
C) radiation. 
D) both conduction and radiation. 
E) both conduction and convection. 
A) conduction. 
B) convection. 
C) radiation. 
D) both conduction and radiation. 
E) both conduction and convection.

Question 20

A slab of insulation is made of three layers, as Drawing I indicates.Each of the layers A, B, and C has the same thickness, but a different thermal conductivity.Heat flows through the slab, and the temperatures are as shown.What are the temperatures T1 and T2 in Drawing II where the layers are arranged in a different order?

Accepted Answer

A) T1 = 230 °C and T2 = 170 °C 
B) T1 = 200 °C and T2 = 180 °C 
C) T1 = 220 °C and T2 = 160 °C 
D) T1 = 180 °C and T2 = 160 °C 
E) T1 = 210 °C and T2 = 190 °C 
A) T1 = 230 °C and T2 = 170 °C 
B) T1 = 200 °C and T2 = 180 °C 
C) T1 = 220 °C and T2 = 160 °C 
D) T1 = 180 °C and T2 = 160 °C 
E) T1 = 210 °C and T2 = 190 °C

Exam 13: The Transfer of Heat

Which one of the following is not an example of convection?

Which of the following materials is the best thermal conductor?

At what rate is heat lost through a 1.5 m × 3.0 m rectangular glass windowpane that is 0.4 cm thick when the inside temperature is 22 °C and the outside temperature is 6.0 °C? The thermal conductivity for the glass is 0.75 W/(m · C°).

Object A has an emissivity of 0.95; and its temperature is 25 °C.At what temperature (in degrees Celsius) does object B, whose emissivity is 0.50, emit radiation at the same rate as object A if both objects have the same surface area?

Which of the following materials is the poorest thermal conductor?

Which one of the following graphs shows the rate at which heat is emitted from a hot body as a function of its Kelvin temperature T?

Suppose you are sitting next to a fire burning in a fireplace.One end of a metal poker has been left in the fire.Which one of the following statements concerning this situation is true?

Complete the following statement: The space between the inner walls of a thermos bottle is evacuated to minimize heat transfer by

A blue supergiant star has a radius of 7.4 × 1010 m.The spherical surface behaves as a blackbody radiator.If the surface temperature is 2.4 × 104 K, what is the rate at which energy is radiated from the star?

Complete the following statement: The interior of a thermos bottle is silvered to minimize heat transfer due to

Two cylindrical steel rods A and B have radii of 0.02 m and 0.04 m, respectively.The two steel rods conduct the same amount of heat per unit time for the same temperature differences between their two ends.What is the ratio of the lengths of the rods, LA/LB?

A beaker of water is placed on a Bunsen burner.As the lower layers of water are heated, they become less dense and rise.This permits cooler layers to move downward and be heated.Eventually, the water boils.Which method(s) of heat transfer is (are) primarily responsible for boiling the sample?

Complete the following statement: Most of the heat that is lost to space from the earth occurs by

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A blue supergiant star has a radius of 7.4 × 10¹⁰ m.The spherical surface behaves as a blackbody radiator.If the surface temperature is 2.4 × 10⁴ K, what is the rate at which energy is radiated from the star?

Two cylindrical steel rods A and B have radii of 0.02 m and 0.04 m, respectively.The two steel rods conduct the same amount of heat per unit time for the same temperature differences between their two ends.What is the ratio of the lengths of the rods, L_A/L_B?