# Electromagnetism- Exam 3

version from 2016-10-15 23:41

## Section 1

What does the magnetic field do?Makes electricity
LodestoneRock swings back and fourth on string
Dipoleas an electron spins around a nucleus it also spins on its own axis. Making a magnetic field.
What creates a magnetic field?Any charged particle in motion.
When a electron spins on its own axis it is known asA magnetic moment or dipole

## Section 2

SI unit of magnetic flux=Weber
Standard unit of magnetic flux density=Tesla and Gauss
1 Weber = _ lines of flux10^8
1 Tesla= _Gauss10^4
Earth's magnetic field in tesla10^-4
Earth's magnetic field in lines of flux10^6
Earth's magnetic field in Gauss1

## Section 3

Every magnet createslines of force
Lines of force travels _ to _ outside of magnetNorth to South
Lines of force travels _to_ inside of magnetSouth to North
Two laws of magnetismOpposites attract and Likes repel
Inverse square lawforce between two charges is directly proportional to the product of their magnitudes; inversely proportional to the square of the distance between them
Inverse square law equationI1/I2= d1/d2

## Section 4

Magnetic InductionAbility to magnetize certain materials when brought into a magnetic field
ClassificationThe ease to which material can be magnetized and ability to remain magnitized
Ferromagneticsimple, easy to magnetize
Paramagneticweak, harder to magnetize
Diamagneticrepels magnetic field
Nonmagneticcannot be magnetized

## Section 5

Natural magnetslodestone- created when iron oxide remains in the earths magnetic field
Artificial Permanent magnet when steel allow is heated and subjected to strong magnetic field, when cooled the alloy is magnetized
Electromagnetsmagnetic field created by moving electric current- temporary

## Section 6

Hand ruleshows where the electrons flow and current flows
ConductorLeft hand shows electron flow
Solenoid/ PolesLeft hand shows electron flow
GeneratorLeft hand shows electron flow
MotorRight hand shows electron flow

## Section 7

SolenoidA current which flow through a series of loops- coil of wire w/ electricity
Electronmagnetin middle of coil of wire
what determines the strengthDiameter, length, and current
Three ways to create an electrical field with magnetsmove conductor through magnetic field, move line of force through a conductor, vary strength from a magnet through a conductor

## Section 8

Farraday's Law4 factors regulate the strength of induced current when magnetic lines of force meet a conductor
What are the 4 factors of Farraday's law?Strength, speed, angle, and number of turns in the conducting coil.
Lenz's LawAn induced current sets up a magnetic field opposing the action that produced the original current
Mutual Inductioncurrent applied to a primary coil induces a current in a secondary coil
Self Inductionmove conductor through coil
Inductive rectancecurrent reverses that tendency for the current to be opposed sets up an opposing forces (potential difference and resistance)
Direct currentone direction
alternating current both directions, produced when lines of force are reversed

## Section 9

Generatorconverts mechanical to electrical energy
Another word for generatordynamo
Armaturecoil of wire (conductor)
Generator consists ofAn armature and a set between two opposing magnetic poles
Slip ringsallow circuit to main stationary while the armature turns
What creates alternating current?When an amature turns
Sine waveone complete turn of armature represents one cycle
The frequency of the sine wave is determined bythe number of cycles per second
1 Hz= _cps1 cps
AC generator resistance=Impedance
Impedance equationI=V/Z (ohm's law)

## Section 10

Motorelectrical to mechanical energy
DC uses what ringscommutator rings
AC uses what ringsslip rings
commutator ringused to pass the electricity into the armature; acts as a switch to keep the flow in the same direction
Synchronous alternating motor keeps going (complete) in timer
Induction motorkeep things outside creates motion inside (anode)
Ametermeasures current in a series
Voltmetermeasures voltage in parallel
Dynameterused w/ AC current to measure current when electromagnets are used
Transformerchange voltage and by doing so change current uses mutual induction(AC current)
StatorMagnets around a rotor, changes current direction
Step up transformermore in secondary than primary high voltage low current
Step down transformermore in primary than secondary low voltage high current

## Section 11

Air transformertwo coils of wire in proximity
Open transformertwo coils in iron case
Closed transformertwo coils of wire enclosed
Shell transformerclosed with two coils of wire converging
Auto transformersingle coil acting as primary and secondary

## Section 12

I^2R losscopper loss; caused by resistance to the current flow
Hysteresis losslagging loss; due to changing of AC field
Eddy current heat loss; due to exchange of equal and opposing forces
Transformer lawvoltage is directly proportional to the number of voltage coil windings
Current and voltage have a what kind of relationshipinversely related
Transformer law equationVp/Vs=Np/Ns; Ns/Np=Vs/Vp=Ip/Is
Transformer ratio is alwayssecondary to primary
Step down ratio factor is alwaysless than one
Step up ratio factor is alwaysmore than one