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# Chapter 1 Energy and Power - PowerPoint PPT Presentation

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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## PowerPoint Slideshow about ' Chapter 1 Energy and Power' - prescott-pollard

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Presentation Transcript

• 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)

• (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

• 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)

The Chevy Volt

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.

• 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!

• 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

Recall that KE = 1/2 mv2

• Fragment G:

• 1 km diameter

• 2000 kg/m3

• 60 km/s

• 1000 Giga-tons of TNT