AC Electricity 02/07/2008

Lecture 7 1

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UCSD: Physics 121; 2012

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power plant home appliance

long transmission line

looks like: Rload

Rwire

Rwire

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UCSD: Physics 121; 2012

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120 Watt Light bulb

12 Volt Connection Box

Power Plant on Colorado River

150 miles

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UCSD: Physics 121; 2012

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AC Electricity 02/07/2008

Lecture 7 2

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UCSD: Physics 121; 2012

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UCSD: Physics 121; 2012

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High Voltage Transmission Lines Low Voltage to Consumers

step-up to 500,000 V

step-down, back to 5,000 V

step-down to 120 V

~5,000 Volts

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UCSD: Physics 121; 2012

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three-phase “live” wires

500,000 230,000 138,000 69,000 7–13,000 long-distance neighborhood

to house

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UCSD: Physics 121; 2012

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AC Electricity 02/07/2008

Lecture 7 3

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UCSD: Physics 121; 2012

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looks just like a magnet

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UCSD: Physics 121; 2012

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If the primary wires and secondary wires don’t actually connect, how does the energy get from the primary circuit to the secondary circuit?!

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UCSD: Physics 121; 2012

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transformers usually heavy due to iron core

AC Electricity 02/07/2008

Lecture 7 4

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UCSD: Physics 121; 2012

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= 170 Volts

= -170 Volts

120 VAC is a root-mean-square number: peak-to-peak is 340 Volts!

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UCSD: Physics 121; 2012

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