Heat and Work: Part 1
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Heat
Work
First Law of Thermodynamics
Temperature and Heat
How Heat is Transferred
Energy in the News
Special Section of Wall Street Journal
Lessons Learned from California:
• Electricity is unique-delivery simultaneous
• Utilities-long term contracts needed
• Generating capacity-need enough, not too
much
• Consumers-no insulation from price changes
• Regulators-must stay current
US Household Energy Use
First Law of Thermodynamics
• Total Energy (E) = Sum of All Energy
• Types of Energy?
• Two ways to change energy content (if no
mass involved)
• 1) Do work
• 2) Add heat
Heat and Work
First Law Summarized
• Work done + Heat Added =
• Change in Energy of the System
• Sum Up Changes (Delta)
Bicycle Pump
Movement of a Piston
Piston moves up and gas under piston is decompressed. Result
is that the gas gets cooler (the gas loses energy). Energy is
transferred from the gas to the outside. In a car this energy moves
the crankshaft and then the wheels of the car.
Temperature Scales
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What is temperature?
Fahrenheit Scale
Centigrade Scale
Kelvin Scale
Equal at what temperature?
Historical Basis
Relationship of Temperature and
Heat
• Q= M*C*Delta T
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Q=heat
C=specific heat
Delta T=change in temperature
M=mass
Reference Points for Temperature
Specific Heats
What substances
Are the best insulation?
Why?
What substances
conduct heat well?
Why?
Thermal Energy (Thermal Mass)
Passive Solar Houses: How Applicable?
Energy in Water Phase Change
Water Phase Change-Another
Picture
Heat Transfer
• What are the three methods of heat transfer?
Conduction
Heat Flow Equation
• Q/t = k*A* (T2-T1)/delta
Convection
• Convection currents in a pan on a hot stove.
Mechanically Aided Convection
Passive Convective System
• What do you think they mean by passive
and active solar heating?
Insulation: How it works
Light: The Spectrum
Visible Light
=small
portion of
electromagnetic
spectrum
Other parts:
infrared
ultraviolet
radio
Where is infrared/
ultraviolet on
this picture?
Emission or Radiation of Heat
Spectrum-Detailed Divisions
Earth and Sun Radiate
Differently
Emissivity of Windows
Low e film on windows-how does it work?
All Three Methods at Once
Energy Savings from Thermostat
Changes
Solar Heater: Active or Passive?
Efficient Windows: How do they
work?
Why argon gas between panes?
Why have triple panes?