lec14 - R = Resistance of the coil • Eddy Currents –...

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Generator vs Motor Counter torque in a Generator When the generator is connected to an external load, •A counter torque on the rotating coil results from the induced current interacting with the magnetic fields. • The applied torque needs to overcome the counter torque to keep the coil rotating at constant angular speed. • The mechanical energy due to the applied torque is converted to electrical energy. When the generator has no load connected to it, there is no induced current in the coil, thus no counter torque. It takes no work to turn the coil. Back EMF in a Motor When the motor is running, a Back EMF ( ε ) in the coil results from the changing flux through the coil. The back EMF limits the magnitude of the current in the coil. R V I = V = Applied EMF = Back EMF
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Unformatted text preview: R = Resistance of the coil. • Eddy Currents – electric currents that arise in a piece of conductor when the magnetic flux is changing through it • A Transformer is a device used to step up or down an AC voltage. – The transformer equation results from Faraday’s law. • A step-down transformer ( V P >V S ) requires N P >N S • A step-up transformer ( V P <V S ) requires N P <N S – If transformer is 100% efficient, (no power is lost due to eddy current) input power equal output power Primary coil ( N P turns) Secondary coil ( N S turns) P V S V Laminated iron core to trap and guide magnetic flux. Lamination eliminates eddy current S S P P V I V I = More Applications of Faraday’s Law P S P S N N V V = Transformer equation...
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This note was uploaded on 12/06/2011 for the course PHYSICS 111&112 taught by Professor Unknown during the Spring '11 term at Ohio State.

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lec14 - R = Resistance of the coil • Eddy Currents –...

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