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Published byElvin Thomas Modified over 9 years ago
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Generator and Transformer
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Moving Conductor If a straight conductor is moved in a path perpendicular to a magnetic field, a current is induced in the conductor Induced emf = B l v l – length of conductor v – velocity of conductor
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Example An airplane travels at 1000 km/hr in region where the Earth’s magnetic field in 5.0 x 10 -5 T. What is the emf induced between the wing tips that are 70m apart?
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Generators (Dynamo) Transforms mechanical energy into electric energy Coil of wire spins in the presence of a permanent magnetic field Induces are current in the coil Current produced actually fluctuates as the coils position in the field changes Max current when perpendicular to B Min current when coil parallel to B (no current)
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Moving Electricity How does electric energy transmit over large distances? How much power is wasted when 10000W of power is transmitted along a cable with a resistance of 1 at 200V? What would be lost if transmitted at 2000V instead? Much less lost when travels at a higher V and lower I
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Transformer Device that changes voltages Two coils around an iron core Current supplied to the primary coil induces a current in the secondary coil By varying the number of windings in the coils you can vary the potentials
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Types Step-up – more windings on the secondary coil increases the voltage Step-down – less windings on the secondary coil decreases the voltage Transformers work only on AC current. Why?
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Transportation Electric energy is stepped up for transmission and then stepped down for household use Most transformers are close to ideal (100% efficient) - low resistance - very permeable rounded core
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