Heat and Work: Part 1 • • • • • 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 • • • • • • 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 • • • • 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?