Download U3g L4 4-24 Test Review

April 24, 2008
DRILL
•
Get with a partner and go over your solutions to the
3G and 3F Test Review. Pay particular attention to #9
on the Fluid Technology side.
•
You have ~12 minutes.
Test Review
TEST FRIDAY – Unit 3F and Unit 3G
(Fluid and Thermal Technology)
Test Review
Test 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.
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Test 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…
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Test Review Solutions
2. 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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Test 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
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Test 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
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Test 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 _____________________.
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Test 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 / Basketball
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:
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Test Review Solutions
1. What must be constant for Boyle’s Law to be usable?
_______________________
Temperature
2. Using gas to apply force or to transport is a particular
type of fluid technology called _____________________.
Pneumatics
3. Using a liquid to apply force or to transport is a particular
type of fluid technology called _________________.
Hydraulics
4. Why is aerodynamics considered fluid technology?
Aerodynamics deals with the motion of air and other
gaseous fluids and with the forces those fluids have on
objects.
5. What are two things that fluid systems have in common?
Test Review
1) Fluids
2) A pressure difference
Test Review Solutions
6.
Show mathematically why you would rather someone push against
you with 10 lbs. of force on a 50 square inches piece of wood than
with a 0.0031 square inch pinhead. (Hint: calculate the pressure of
each)
1) Write given information:
F = 10 lbs
A1 = 50 in2
A2 = 0.0031 in2
P1 = ?
P2 = ?
2) Write formula and solve:
P1 = F1 / A1
P2 = F2 / A2
= (10 lbs) / (50 in2 )
= (10 lbs) / (0.0031 in2 )
P1 = 0.2 psi
P1 = 3225.8 psi
I would rather someone use a block of wood
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since the pressure is MUCH less.
Test Review Solutions
7.
Based on what we covered in the Fluid Technology unit, there are
at least two ways to correctly label the axes of each of the graphs
below. Do so.
P
P
or
or
V
V
V or P
(Inversely Proportional)
1/V or 1/P
(Proportional)
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Test Review Solutions
8.
There are two ways to mathematically express the relationship
between volume and pressure. Do so and explain. (Hint:
Pressure and volume are inversely proportional.)
V a 1/P
or
P a 1/V
[Volume is
proportional to 1/P]
[Pressure is
proportional to 1/V]
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Test Review Solutions
9.
On a separate sheet of paper write three new, different problems
related to fluid technology. Use your previous problem sheet for
examples. One problem should require use of the basic P = F / A
formula. One problem should be a simple Boyle’s Law problem.
One problem should use the diagram below. After writing these
three problems, solve them.
Test Review
1. With a partner, identify 3 examples of Conduction,
Convection, and Radiation (total 9 examples) not
discussed in class.
2. Describe your observations of the heat transfer in
each example.
3. Describe what is causing the heat transfer in each
example.
Test Review