AC Electricity 02/07/2008 Lecture 7 1 Winter 2012 UCSD: Physics 121; 2012 2 power plant home appliance long transmission line looks like: Rload Rwire Rwire Winter 2012 UCSD: Physics 121; 2012 3 120 Watt Light bulb 12 Volt Connection Box Power Plant on Colorado River 150 miles Winter 2012 UCSD: Physics 121; 2012 4AC Electricity 02/07/2008 Lecture 7 2 Winter 2012 UCSD: Physics 121; 2012 5 Winter 2012 UCSD: Physics 121; 2012 6 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 Winter 2012 UCSD: Physics 121; 2012 7 three-phase “live” wires 500,000 230,000 138,000 69,000 7–13,000 long-distance neighborhood to house Winter 2012 UCSD: Physics 121; 2012 8AC Electricity 02/07/2008 Lecture 7 3 Winter 2012 UCSD: Physics 121; 2012 9 looks just like a magnet Winter 2012 UCSD: Physics 121; 2012 10 Winter 2012 UCSD: Physics 121; 2012 11 If the primary wires and secondary wires don’t actually connect, how does the energy get from the primary circuit to the secondary circuit?! Winter 2012 UCSD: Physics 121; 2012 12 transformers usually heavy due to iron coreAC Electricity 02/07/2008 Lecture 7 4 Winter 2012 UCSD: Physics 121; 2012 13 Winter 2012 UCSD: Physics 121; 2012 14 = 170 Volts = -170 Volts 120 VAC is a root-mean-square number: peak-to-peak is 340 Volts! Winter 2012 UCSD: Physics 121; 2012 15 Winter 2012 UCSD: Physics 121; 2012
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