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Transcript
Generator and Transformer 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 =Blv l – length of conductor v – velocity of conductor 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? 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) 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 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 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? 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
