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Induction Faraday’s Experiment Magnetic Flux Faraday’s Law Electrical Generator Lenz’s Law Alternating Currents Generators Transformers Resistors in AC Circuits Capacitors in AC Circuits Inductors in AC Circuits LC Circuits Transformers Most practical transformers have central regions filled with a magnetic material. This produces a larger flux, resulting in a larger voltage at both the input and output coils. However: V out V in = constant Φ out = N out N in Φ in V out = N out N in V in Transformers cannot change DC voltages!
College Physics B Review: Force on a Particle Magnetic Induction Faraday’s Experiment Magnetic Flux Faraday’s Law Electrical Generator Lenz’s Law Alternating Currents Generators Transformers Resistors in AC Circuits Capacitors in AC Circuits Inductors in AC Circuits LC Circuits Transformers At the power plant Supply voltage of about 5 000 V Cross-country lines Voltage of about 500 000 V
College Physics B Review: Force on a Particle Magnetic Induction Faraday’s Experiment Magnetic Flux Faraday’s Law Electrical Generator Lenz’s Law Alternating Currents Generators Transformers Resistors in AC Circuits Capacitors in AC Circuits Inductors in AC Circuits LC Circuits Transformers and Power Transformers are used in the transmission of electric power over long distances: Many household appliances use transformers to convert the AC voltage at a wall socket to the smaller voltages needed in many devices. The output voltage of a transformer can also be made much larger by arranging the number of coils. According to the principle of energy conservation, the energy delivered through the input coil must either be stored in the transformer’s magnetic field or transferred to the output circuit: The power delivered to the input coil must equal the output power.
College Physics B Review: Force on a Particle Magnetic Induction Faraday’s Experiment Magnetic Flux Faraday’s Law Electrical Generator Lenz’s Law Alternating Currents Generators Transformers Resistors in AC Circuits Capacitors in AC Circuits Inductors in AC Circuits LC Circuits Transformers and Power According to the principle of energy conservation, the energy delivered through the input coil must either be stored in the transformer’s magnetic field or transferred to the output circuit: Since P = V I , if V out is greater than V in , then I out must be smaller than I in . P in = P out only in ideal transformers In real transformers, the coils always have a small electrical resistance causing some power dissipation. For a real transformer, the output power is always less than the input power. Power carried by the power line: P avg = V rms I rms
College Physics B Review: Force on a Particle Magnetic Induction Faraday’s Experiment Magnetic Flux Faraday’s Law Electrical Generator Lenz’s Law Alternating Currents Generators Transformers Resistors in AC Circuits Capacitors in AC Circuits Inductors in AC Circuits LC Circuits Example An AC power line operates with a voltage V rms = 500 , 000 V and carries an AC current with I rms = 1000 A.

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