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# electromagnetism

studies the force associated with e- in motion electromagnetism
what are the ways we can induce current to flow within a conductor, as long as there is a potential difference * moving conductor across a stationary magnetic field * cut a stationary conductor with magnetic lines of force * place a stationary conductor with a varying magnetic flux
what is Faraday's law an electric current is induced to flow in a circuit if some part of the circuit is in a changing magnetic field
what factors control the amount of current generated within a conductor * strength of magnet * speed or velocity of magnetic field past conductor * angle at which the magnetic field cuts the conductor * # of turns in conductor
when a conductor is perpendicular to the magnetic field, there is _______ current flow and when the conductor is parallel to the magnetic field there is _______ current flow * no * maximum
what is Lenz's law induced current flows in a direction that is opposite the action that induces it
what are the devices that work using electromagnetic induction * helix * solenoid * elctromagnet
helix coil of wire (ex. tube filament)
solenoid coil of wire connected to source and carries current which sets up a magnetic field (ex. locks- bucky, detent, tube)
electromagnet coil of wire carrying a current with an iron core (ex. remote control device, detent locks, fire doors
uses a single coil of wire with constant potential difference elctromagnetic self induction
what is the purpose of the autotransformer sits on the primary side of circuit/kVp selector/works off EM self induction
uses two coils of wire(primary and secondary)/step up or step down electromagnetic mutual induction
*potential difference creates current flowing *sets up magnetic field that cuts through 2nd coil to induce opposing potential difference and induced current primary coil
*carries induced current *induced current creates magnetic field around 2nd coil that cuts 1st coil to keep current flowing *no moving parts or contact secondary coil
step up (high tension) transformer works off EM mutual induction/ increases voltage to kVp/ decreases amperage to milliamps(to prevent blowing trasformer)/ more turns on secondary coil/ high tension transformer
step down (filament) transformer works off EM mutual induction/ decreases kVp to voltage(6-10 volts)/ increases mA back to amperage(3-5 amps for overhead and .5-5 mA for fluoro/ more turns on primary coil/ used to produce filament current/attached to filament of tube on secondary side
converts mechanical to electrical energy generator(dynamo)
converts electrical to mechanical energy *rotor motor
what are the types of transformers, in order from weakest to strongest and what type of induction do they work off of *air core *open core *closed core *shell type **all work of mutual induction
two coils of wire next to each other air core transformer
two coils of wire, each with iron core inside coils open core transformer
two coils of wire, each with its own iron core, the iron cores are connected @ bottom closed core transformer
primary and secondary coil are wrapped around the same iron core shell type transformer
what are the transformer law formulas *Vs/Vp=Ns/Np *Is/Ip=Vp/Vs
what causes transformer inefficiency *resistance *hysteresis *eddy current
loss of power due to heat resistance
loss of power due to changing magnetic field hysteresis
loss of power due to alternating current eddy current
what is done to reduce transformer inefficiency cut and laminate cores