Energy Unit M,F & E Book – Chapters 5 &6

What is Energy? Def: ability to do work or cause change Needed to cause a change in motion Measured in Joules Potential – stored/position Elastic potential energy Gravitational potential energy Weight X Height Kinetic – motion ½ mass x velocity2

Forms of Energy 6 Forms Mechanical Chemical Thermal Nuclear Moving parts Chemical Chemical bonds Thermal heat Nuclear Nucleus of an atom

Conversion – changing from one form to another Electrical electricity Electromagnetic Light, radiowaves, UV, infrared, gamma rays Conversion – changing from one form to another 1st law of thermodynamics: some of the energy is always converted to heat Law of Conservation of Energy Energy can neither be created nor destroyed, but simply changed to different forms

Electrical Energy Energy associated with moving electrons Common conversion: Electric motor  converts electric energy to mechanical energy Electric Battery  converts chemical energy into electric energy Electric Generator  converts mechanical energy to electrical energy Electromagnetic Induction Turbines – large coils of wire that pass through strong magnetic fields

Electrical Energy Ways to Generate Electricity: Coal, Nuclear, Wind, Water, Solar Alternating Current is used to transmit electricity far distances to homes Current changes direction Transformers change voltage Electrical Power – Voltage X Current Watts Electrical Energy – Power X Time Kilowatt-hours

Energy Conversions for Generating Electricity Think about all the conversions that needed to take place before you used an appliance this morning? Appliance? Conversion for Generating Electricity Before that?

Nuclear Energy Fusion – combining two atoms to make 1 Need extremely high temperatures The Sun Cold Fusion? Fission – splitting the atom Nuclear Power and Nuclear Weapons Parts of a Nuclear Power Plant: Reactor Core, Fuel Rods, Cooling Tower Steam is only air emissions Dangerous Radioactive Waste

Electromagnetic Energy Characteristics Travels in electric and magnetic waves Wave Structure Crest, trough and wavelength Speed of energy = 300,000 km/sec Frequency – how many waves go by each second Hertz – wave per second Relationships Shorter the Wavelength: Higher the Frequency Higher the frequency: Higher the energy Higher the energy: More Dangerous

Types of E-M energy Electromagnetic Spectrum Depends on Wavelength List from Long to Short Wavelength Radio waves Microwaves Infrared (heat) Visible Light (ROY B BIV) Ultraviolet (UV) X-Ray Gamma

Thermal Energy Deals with movement of particles in matter Heat vs. Temperature Heat - amount of thermal energy Temperature - average speed of the particles Celsius and Kelvin Scale Absolute Zero Is it possible to have more heat but a lower temperature? Thimble of boiling water vs. Iceburg

Thermal Energy Methods of Heat Transfer  always moves from high heat to low heat Conduction – direct contact Warm seat Convection – carried by fluid currents Gulf Stream Radiation – carried by electromagnetic waves (infrared) Do not need a substance to transfer Sun’s heat through space Conductor – heat transfers easily Insulator – prevents heat transfer Specific Heat – the amount of heat needed to raise the temperature of 1 kg of a substance by 1o Kelvin

Phase Changes Solid, Liquid, Gas or Plasma Depends on kinetic energy of particles Melting/Freezing – change between solid and liquid Water: 0oC (32oF) Boiling/Condensation – change between liquid and gas Water: 100oC (212oF) Evaporation – liquid to gas without reaching boiling point Sublimation – solid directly to gas without becoming a liquid first Dry ice Know how to read Phase Change Graph Sketch the graph on the next slide and label Temperature does not change during phase change

Phase Changes