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Chapter 1 Energy and Power

Chapter 1 Energy and Power. Energy - the ability to do work; anything that can be turned into heat. Several forms: Kinetic KE = 1/2 mv 2 Heat is special form Potential (stored) Can be mechanical (spring), electro-chemical (battery), or electronic (energy stored in excited atoms)

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Chapter 1 Energy and Power

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  1. Chapter 1 Energy and Power • Energy - the ability to do work; anything that can be turned into heat. • Several forms: • Kinetic KE = 1/2 mv2 • Heat is special form • Potential (stored) • Can be mechanical (spring), electro-chemical (battery), or electronic (energy stored in excited atoms) • Gravity is special case PE = mgh • Chemical bonds • “Light” • Mass (Einstein’s famous E = mc2)

  2. Work, Energy, Power, and their units • (Physics) Work = Force x distance • Work and energy have same units • Joules in metric • Foot-pounds in English (seldom used) • 1 Calorie = 1000 calories • Power is the time rate of doing work or the time rate of gaining or losing energy • Units of Power = Joule/sec = Watt • So kWh is a unit of energy • Energy Content Table

  3. Alternative Energy: Gasoline, batteries, and fuel cells • Gasoline is (relatively) cheap, but has problems… • Unreliable and price may go higher • Efficiency, pollution and greenhouse gas production • So what’s wrong with batteries? • Heavy and bulky • Low energy per gram compared to gasoline • Expensive to replace (especially ones with most energy/volume) • Hybrids? • Still problems with batteries • Best with limited use of batteries (they last longer)

  4. But the electric cars are coming! The Tesla Roadster The Chevy Volt

  5. What’s all the hype about hydrogen? • Not mined; made from water using hydrolysis • Fuel cell creates water and electricity • Lower energy/volume than gasoline • Even when compressed (1/6 as much) or liquified (1/3 as much) • Made from methane, but produces CO2 • BUT, hydrogen fuel cells produce no pollution, not even CO2, so there may be conditions under which their use is justified. Just don’t expect a hydrogen car any time soon.

  6. Have an eye on those tables! • Page 1-12 Notice coal and natural gas vs. gasoline • Page 1-16 Examples of energy units • Page 1-18 Examples of power units • These are really good sources of test questions!

  7. Solar Power • About 1 kW shines on 1 m2 • About 1 GW shines on 1 km2 • Take solar cell efficiency into account… • 1 m2 gives 150-400 W of electricity • 1 km2 gives 150-400 MW of electricity • Use hydrogen storage for night energy? • Solar cells are expensive and fragile

  8. Kinetic Energy Killed the Dinosaurs Recall that KE = 1/2 mv2 • Fragment G: • 1 km diameter • 2000 kg/m3 • 60 km/s • 1000 Giga-tons of TNT

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