April 11, 2011
DRILL: Answer whether the heat transfer is
conduction, convection, or radiation
1.
2.
3.
A thermos bottle has a shiny interior.
Radiation
What type of heat transfer does it
prevent?
Heat in the room moves with the warm
Convection
currents from warmer areas to cooler
areas.
Brownies bake in a glass pan using these
2 methods.
Convection(from oven) and
Conduction (through pan)
4.
You feel the heat of a wood stove when
Quiz Review
you stand next to it. Radiation and Convection
Quiz Review Solutions
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 objects
Quiz Review
Quiz Review Solutions
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
Quiz Review Solutions
2. List 3 example of Thermal Technologies and
identify why they are considered a thermal
technology.
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…
Quiz Review
Quiz Review Solutions
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.
Quiz Review
Quiz Review Solutions
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
Quiz Review
Quiz Review Solutions
5. Number the following from 1-5, 1 being coolest and
5 being hottest.
3 Yellow
1 Red
5 White
4 Blue
2 Orange
Remember
ROY G. BIV
Quiz Review
Quiz Review Solutions
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
Higher
__________________
temperature to a region of
__________________
temperature.
Lower
10. The driving force for heat transfer is
______________________________________________
Temperature Difference (Difference of Temperature)
11. The more accurate way of saying an object is “cold” is
Lacks
saying that it ____________
heat.
12. The three methods of heat transfer are
____________________________________________.
Convection, Conduction, Radiation
13. The sun’s heat reaching us through space is an example
Radiation
of the method of _____________________.
Quiz Review
Quiz Review Solutions
14. A car engine cooling system is an example of the method
of _____________________.
Convection
15. Heat from a house in winter travels through the walls by
the method of _____________________.
Conduction
16. Give an example of a technology that combines
chemicals to produce heat: ___________________.
Heat Pads
17. Give an example of a technology that converts
mechanical energy to heat: ___________________.
Car Engine
18. Give an example of a technology that converts electrical
energy to heat: ___________________.
Electric Stove
19. Give an example of a technology that converts light
energy to heat: ___________________.
Incandescent Light Bulb
20. Sketch an example of Conduction, Convection, and
Radiation:
Quiz Review
Quiz Review Solutions
1. How much energy is required to raise the
temperature of 10 grams of water by 40
degrees Celsius?
Step1: Write down
information
E = ??
Step 2: Write down
equation
M = 10 gram
C = 1 cal/(g*Celsius)
DT= 40 degrees Celsius
E  M  C  DT
cal
E  10 g 1
 40Celsius
g  Celsius
E  400cal
Quiz Review
Quiz Review Solutions
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?
Step1: Write down
information
E = 1,000 calories
M = 50 g
C = 1 cal/(g*Celsius)
DT= ??
Step 2: Write down equation
E  M  C  DT
cal
1,000cal  50 g 1
 DT
g  Celsius
1,000cal
DT 
cal
50 g 1
g  Celsius
DT  20Celsius
Quiz Review
Quiz Review Solutions
3. If the starting temperature for problem 2 was 20
Celsius, what was the ending temperature?
Ending Temperature = Starting Temperature
+ Change
Ending Temperature = 20 C+ 20 C
Ending Temperature = 40 C
Quiz Review
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
Quiz Review