Chapter 10: part 2

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Chapter 10 part 2
Ohms Law Superconductivity Parallel and Series
Circuits Delivery of Power in a Circuit Pricing
Energy Fuel Cells
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Energy in the News
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Ohms Law
V I R V voltage, units of volts I
current, units of amperes (coulombs per
second) R resistance, units of ohms
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Physical Meaning
Resistance resistance to flow of
electrons (pipe wire) Voltage electrical
potential ( like pressure head for a pump driving
flow potential energy per unit charge) 1 volt
1 Joule per coulomb Current quantity of
electrons flowing
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Toaster
What is the current?
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Resistive Heating
Power Voltage Current P VI Plug in ohms
law, V I R P I2 R Electric stoves,
toasters and hair dryers What do they have in
common? Expected wattage?
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Electrical Energy Work or Heat
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Superconductivity
Major problem with energy transfer transmission
losses 10 High temperature superconductors
greatly reduce losses High temperature
superconductors-will conduct at
temperatures Achievable with liquid nitrogen
(still pretty cold!!) Ceramics latest
superconductors. Normally insulators.
Structure of ceramics like high pressure
silicates (Walker) High pressure pressure at
LDEO.
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Simple Circuits
Parallel everything connected by the same circle
of Wire Series a set of interconnected
circular circuits
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Meissner Effect
Superconducting materials exclude magnetic
fields Therefore, a magnet near a superconductor
will Stay in the air Result magnetic levitation
(MAGLEV) Bullet trains in Japan and Germany use
MAGLEV
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Series and Parallel Circuits
Parallel circuits Resistances add Series
circuitsCurrents add Household circuits Which
type? Fire danger? How to reduce fire hazard?
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Batteries Series and Parallel
Which arrangement produces More voltage? More
current? More resistance? More power?
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Typical Household Circuit
What should be included to ensure safety?
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Prices of Energy
Typical prices of energy per kilowatt
hour? Locally (on Long Island)? Nationally?
Rates for wind power?
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Payback Time on Energy Efficiency
Energy efficiency is an investment Example
compact fluorescent bulbs Cost 10 each (10
times as much), last 10 times as long Use 1/4
the energy of incandescent bulbs. Payback
timetime to pay back the extra cost for
energy Saving equipment with savings on energy
cost.
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Quote from Prizewinning Engineer
What will the lights of the future be?
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L.E.D.s
Light Emitting Diodes Lumens per Watt Lumens
measure Of light intensity How do
incandescents Mercury, halogens Low pressure
sodium Fluorescents measure Up?
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L.E.D.s How They Work
Semi-conductor N-type layer- Supplies
electrons P-type layer supplies
positive Charges or holes In the active
layer Photons of light Emitted. Solar cells
also use Semi-conductors N and P type layers
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Lighting Whales with LEDs
Cant use visible light? Why? Light is in near
infra-red Visible to videotape but not to
whales LEDS allow selection of wavelength Of
light. LEDS work well at high pressures 1
atmosphere per 10 meters of water
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Common Uses of LEDs
Upper left SGT Pepper costumes Upper
Right Traffic light Lower Right Taillights,
turn signals Lower left signs
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Fuel Cells
Fuel cell combines a fuel ( Often natural gas or
hydrogen) With oxygen. Uses the chemical Energy
to produce electricity. Present cost 3000 to
4000 per Kilowatt too expensive
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Greenhouse Gas Emissions
Why are zero emissions Vehicles (electric cars)
Not necessarily the best Choice?
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Cost for Fuel Cells Medium Term
Life cycle costs cents Per mile Yellow
Fuel Purple Electricity Dark blue
Maintenance Brown Fuel Storage RedBattery Light
blue Fuel Cell GreenBasic Vehicle Cost
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Long Term Costs for Fuel Cells
Life cycle costs cents Per mile Yellow
fuel Purple electricity Dark blue
Maintenance Brown Fuel Storage RedBattery Light
blue Fuel Cell GreenBasic Vehicle Cost
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Types of Fuel Cells
PEM Proton exchange membrane Fuel cell cars
can be refueled in minutes (unlike ZEVs) Range
similar if natural gas or methanol powered, Very
Quiet!! Use 2/5 of energy of typical cars with
internal combustion engines Drawbacks platinum
catalyst in short supply
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Fuel Cell Central Park, New York
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Fuel Cell Powered Bus
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Fuel Cells The Future
Daimler/Chrysler and General Motors Fuel cell
powered car By 2004. Honda Fuel cell powered
car by 2003. Roughly 2.5 to 3 times as
efficient as typical gasoline powered cars. Wind
farms on 6 of land in Great Plains enough to
produce hydrogen For all USA cars and light
trucks if all fuel cell powered!! Photovoltaic
cells (solar cells) on 1 of US land needed to
provide hydrogen for US Fuel cell fleet.