electromagnetism

who invented the battery

volta

who discovered that an electric current produces a magnetic field

oersted

who discovered that current is induced by a moving magnetic field

faraday

what is the law that states: the induced current flows in the opposite direction of the applied current

lenz law

what is the right thumb rule

direction of the thumb=direction of current; direction of fingers=direction of magnetic field

what is a solenoid

helix with a current

what is a helix

coil of wire

what is an electromagnet

solenoid with an iron core

what is self induction

the changing current creates a changing magnetic field, which induces a voltage that opposes the original change in current, following Lenz's Law

what is mutual induction

magnetic field induces a current in a nearby helix

what are the forms of power loss

copper, hysteresis, eddy current

how is hysteresis a power loss

rearranges magnetic domains

what is an eddy current

swirling currents in the core, minimized by lamination of plates

what is the result of no motion of a magnet or wire when trying to induce a current?

no current

what converts mechanical energy to electrical energy

a generator

how does an autotransformer accomplish voltage regulation

submerged in oil to reduce shockwave

what happens to a generator if the magnetic field is increased? decreased?

Increased magnetic field: The generator produces more voltage (higher output).

Decreased magnetic field: The generator produces less voltage (lower output)

direct relationship

what transformer is used in modern x-ray equipment

step up and step down transformer; shell transformer

what is a step up & step down transformer

used to change the magnitude of current and voltage; mutual induction

how does a step up transformer operate

found in tube circuit; primary power→ secondary power, less coils→ more coils, power increase

how does a step down transformer operate

found in filament circuit; primary power → secondary power, more coils→ less coils, power decrease

what is the relationship between the number of loops in a generator and current

a higher number of loops directly correlates to a higher induced current; directly proportional

what magnetic field angle will give the most intensity (current)

90º

what is an air core transformer

not very efficient, only two coils

what is an open core transformer

addition of an iron core increases the strength of the magnetic field

what is a closed core transformer

closed iron core

what is a shell type transformer

most efficient; 95% efficient

what converts electrical energy to mechanical energy

a motor

what type of motor does the rotating anode use

induction motor; stator and rotor

what are the two motor types

synchronous and induction

what is a synchronous motor

coil rotates at same frequency as current; used in timing circuits in older x-ray machines

what is a induction motor

stator and rotor; uses electromagnets to create magnetic field to interact with current’s magnetic field

what is potential difference

electromotive force (voltage), force that causes charges to move; electrical push or pull

what is the transformer law: voltage formula

Vp/Vs=Np/Ns

what is the transformer law: amperage formula

Is/Ip=Np/Ns

how many cycles/second does an alternating current generator operate with at 60 Hz and 120 alternations (impulses)

a frequency has 60 Hz therefore 60 cycles/second, each cycle has 2 alternations therefore 60Hz has 120 alternations