April 11, 2011DRILL: Answer whether the heat transfer is

conduction, convection, or radiation

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1. A thermos bottle has a shiny interior. What type of heat transfer does it prevent?

2. Heat in the room moves with the warm currents from warmer areas to cooler areas.

3. Brownies bake in a glass pan using these 2 methods.

4. You feel the heat of a wood stove when you stand next to it.

Radiation

Convection

Convection(from oven) and Conduction (through pan)

Radiation and Convection

Quiz Tomorrow on Thermal Technology

Take out review sheet

Movie on Wednesday/Thursday

-There will be an assignment, so you must pay attention

Bookwork if disruption/throwing objectsQuiz Review

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1. Define the following– Thermal Technology – the technology of producing,

storing, controlling, transmitting and getting work from heat energy.

– Thermodynamics - the science dealing with internal energy, heat, and work

– Photon – a particle of light– Conduction – the transfer of heat through a

substance by collision of molecules.– Convection – is the transfer of heat by movement of

a fluid.– Radiation – the transfer of energy by

electromagnetic waves. Quiz Review

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2. List 3 example of Thermal Technologies and identify why they are considered a thermal technology.

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Example applications: • Furnace, • Hot water heater, • Toaster, • Insulation, • Heat exchanger, • Refrigerator, • Hot air balloon,• Fan,• Engine cooling system,

• Oven,• Blow-dryer,• Thermos,• Heat shrink,• Styrofoam,• Radiator,• Blanket,• Winter jacket,• Wool socks…

3. What is the purpose of using infrared photography if hot objects are often red to our eyes?

The more powerful radiation heat is in the form of infrared light, which we cannot see with our natural eyes. Therefore, infrared photography allows us to “see” the heat given off by objects even if the material is not hot enough for there to be a color change.

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4. What are the two types of convection? Explain each.

• Natural Convection– Fluid surrounding a heat source receives heat

and rises (due to lower density)– Surrounding cooler fluid moves in to replace it.– Cooler fluid is heated, rises, and cycle continues.

• Forced Convection– Fans or other means are used to propel a fluid.– An convection current is induced.– Car engine and A/C are examples

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5. Number the following from 1-5, 1 being coolest and 5 being hottest.

Yellow

Red

White

Blue

Orange

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1

2

3

5

4

Remember ROY G. BIV

6. (Solid / Liquid / No Medium) is the medium for conduction.

7. (Solid / Liquid / No Medium) is the medium for convection.

8. (Solid / Liquid / No Medium) is the medium for radiation.9. Thermal energy always travels from a region of

__________________ temperature to a region of __________________ temperature.

10. The driving force for heat transfer is ______________________________________________

11. The more accurate way of saying an object is “cold” is saying that it ____________ heat.

12. The three methods of heat transfer are ____________________________________________.

13. The sun’s heat reaching us through space is an example of the method of _____________________. Quiz

Review

Quiz Review Solutions

HigherLower

Temperature Difference (Difference of Temperature)

Lacks

Convection, Conduction, Radiation

Radiation

14. A car engine cooling system is an example of the method of _____________________.

15. Heat from a house in winter travels through the walls by the method of _____________________.

16. Give an example of a technology that combines chemicals to produce heat: ___________________.

17. Give an example of a technology that converts mechanical energy to heat: ___________________.

18. Give an example of a technology that converts electrical energy to heat: ___________________.

19. Give an example of a technology that converts light energy to heat: ___________________.

20. Sketch an example of Conduction, Convection, and Radiation:

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Convection

Conduction

Heat Pads

Car Engine

Electric Stove

Incandescent Light Bulb

1. How much energy is required to raise the temperature of 10 grams of water by 40 degrees Celsius?

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Step1: Write down informationE = ??

M = 10 gram

C = 1 cal/(g*Celsius)

DT= 40 degrees Celsius

Step 2: Write down equation

TCME

CelsiusCelsiusg

calgE 40110

calE 400

2. A microwave supplies 1,000 calories of energy to 50 grams of water. The heat capacity is 1 cal/(g Celsius). How much did the temperature increase?

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Step1: Write down information

E = 1,000 calories

M = 50 g

C = 1 cal/(g*Celsius)

T= ??

Step 2: Write down equation TCME

TCelsiusg

calgcal

150000,1

Celsiusgcal

g

calT

150

000,1

CelsiusT 20

3. If the starting temperature for problem 2 was 20 Celsius, what was the ending temperature?

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Ending Temperature = Starting Temperature + Change

Ending Temperature = 20 C+ 20 C

Ending Temperature = 40 C

1. With a partner next to you, identify 3 examples of Conduction, Convection, and Radiation (total 9 examples) not discussed in class.

2. Explain how each energy is transferred in each example

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