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Chapter 1 Energy and Power

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Chapter 1 Energy and Power - PowerPoint PPT Presentation


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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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slide1

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)
slide2

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
slide3

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)
slide4

But the electric cars are coming!

The Tesla Roadster

The Chevy Volt

slide5

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.
slide6

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!
slide7

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
slide8

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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