Magnetism hand-written notes Flashcards
magnetic deviation
magnetic northpole ___
down
compass need points to magnetic ___ pole
south
Outside magnet (___ to ___ )
north to south
Inside magnet (___ to ____ )
south to north
Lines of flux (___ to ___ )
north to south
Lines of flux qualities:
-possess ____ (north to south)
-they never ___ (repel each other)
-attracted to ___ (pole), accumulates at poles before spreading out
-continuous (no ___ or no ___)
-goes to easiest ____
direction, cross, core, beginning, end, route
Magnetic molecules or magnetic ____
domains
Magnetic Materials
-____ materials
-____ materials
-____ materials (copper, brass, and antimony
Ferromagnetic, Paramagnetic, Diamagnetic
More magnetic materials:
-___ magnet: magnetic ink, ferrite that is powdered, rubber, plastic, and liquid
-___ S, best permanent magnet (aluminium, nickel, cobalt, copper, and iron)
-____: insulators that’s 1,000,000 ohms cm (barium and strontium ferrites)
ceramic, Alnico, Ferrite
Magnetic lines of force
-___
-lines of ___
Flux
Basic Law of magnetism: unlike poles ____ and like poles ___
-south ___ north, north ___ north and south ___ south
attract, repel, attract, repel
Electromagnetics
-If a conductor is wound into a coil. The magnetic lines of flux ___ to produce ___ magnetic field
-dot: current flowing ___
-cross: current flowing ___
add, stronger, out, in
What factors determine magnetic field strength?
-___ current flow ____ magnetic field strength
______ (# of turns of wire times current flow
increases, ampere-turns
Earth rotate on ___ pole
axis
natural magnetics - ____ or ____
___, ____, and ____ - natural magnet
leading stones, lodestone, iron, nickel, and cobalt
______, bunch of tiny magnet
magnetic domain
_____, divert magnetic force
Magnetic screen
____: the property that opposes the setting up of flux lines
Reluctance goes ____, the ___ magnetic flux lines going through it (resistance) iron
____ iron - maintain lines of flux magnetic induction (permanent magnet). Need stronger field
___ iron - loses lines of flux (Get magnetized easily)
Reluctance, down, more, hard, soft
How to increase magnetic properties?
Align magnetic domains (artificial magnets)
Three ways to increase magnetism?
-_____ increase
-____ in same direction
- ___ and tap
electric current, stroking, align
tighter the coil and more turns ___ magnetic flux
left hand rule
more
Core base material the coils can wound around.
-___-core magnet (wood or plastic) non-magnetic material
-___-core magnet (iron or soft- steel)
Core base materials can increase strength of magnet by having magnetic materials in the center
air, iron, center
3 Ways to demagnetize
-____ (AC)
-___ -(currie temperature). Each object has it’s own currie temperature.
-___ (or tapping). Demagnetize after stop tapping
electrical current, heat, vibration
____ - keep it from being distorted by other magnetic fields. (cloth and iron)
Keeper
Core material
-_____: ability to become magnetized (increase # of flux lines produced, more ampere turns, and more permeability)
-____: resistance to being magnetized
-____: when magnet strength doesn’t increase much with more current flow increased (require larger piece of core material
permeability, reluctance, saturation
____ - magnetism left in core material after stopping current flow
____ - retain magnetism ability
Coercive force goes ___, Residual magnetism goes ___
Residual magnetism, Coercive force, up, up
Magnetic measurement: measure magnetic field strength
-____ system
CGS system
-____ or SI system
English, MKS
___ (flux density), Magnetic strength (lines per square inch) = Flux lines/ Area
Beta
mmf (___, ampere-turns), Total force producing magnetic field or flux = Flux lines times reluctance
magnetomotive force
___ (in pounds) = Beta (flux density in lines per square inch) times A (area of the magnet)/ 72,000,000
Pull
dot and cross
dot (___)
cross (___)
use left hand, thumb is north
fingers close towards over and under to flux directions
CW, ccw
Magnetic Measurement:
The ___ system (centimeter gram- second) system
-____ (one magnetic line of force)
-___ (magnetic force of 1 maxwell per square centimeter) or also, ____ lines of flux per square inch
-_____: magnetomotive force measurement
Conversion
1 gilbert = ___ ampere-turns
1 ampere-turn = ____ gilbert
CGS, maxwell, gauss, 6.4516, gilbert, 1.256, 0.7905
The ___ or SI system (metre- kilogram - second) system
-unit of force newton
- one newton = ____ pounds
-____ newtons - 1 pound of force
-weber: measure magnetic flux
-one weber - _____ lines of flux or 10 to the power of 8 maxwells
MKS, 0.2248, 4.448, 100,000,000
____: ability to be magnetized (# number of flux lines produce goes up, more ampere turns goes up). Likely proportional to having more flux lines by coil and current flow.
If core material makes magnetic field 10 times stronger. Core materials have a permeability of __.
-Soft iron or steel (permeability goes ___ and reluctance goes ___. Easily magnetized)
-Copper (permeability goes ____ and reluctance goes ___. Less lines of flux going through it.
-____: when all molecules of the magnetic material are lines up
Permeability, 10, up, down, down, up, Saturation
____: amount of remaining magnetism left after magnetizing force stopped.
Ex. stopping current flow.
Coercive force goes ___ when residual magnetism difficult to remove
-Permanent magnets (coercive force goes __)
-Electromagnets (coercive force goes ___)
____ (retentivity): how much current flow in opposite direction needed to remove residual magnetism
Residual magnetism, up, up, down, Coercive force
Flux loops continue to formed adjacent outwards as increase current
True or False
current consistent and flux lines stationary
current decrease and flux lines collapse in centre
distance goes __, then the amount of flux lines goes ___
True, up, down
Conductors in parallel going in same directions ___, and joins in one loop.
repel conjoins in space broken
attract
Magnitude - The magnitude of the force between parallel conductor
Fm - k x I x I/ d power of 2 (two conductors)
True or False
True
tightly coiled, lines of flux go less in core mostly magnetic force loss
True or False
-spiral shaped coil- ___
-____- moving core, attracts or repels moving core
True, helix, solenoid
Electromagnet strength factors?
-___ (enamel to reduce)
- ____ goes down and strength goes down
-____ and turns #1
-magnetic strength (turns times amps (primary no need to disconnect)
-core that is ferromagnetic material (iron strengthen flux density and magnetic field)
-anything not ferromagnetic material (doesn’t do anything, such as wood and copper)
air gaps, flux density, magnitude
Electromagnetic series with rheostat (variable resistor) usually for motors, lifting device, and generators.
True or False
Change flux density and strength of magnet
True
Magnetic circuits ( flux lines complete loop)
-magnetic flux goes ___, magnetomotive force goes ___, and reluctance goes ___
Flux lines = Fm/ Rm
Magnetomotive force (mmf) = number quantity of mmf = Fm
-unit (amp-turn per weber)
up, up, down
Reluctance goes ___ and length goes ___, reluctance goes ___ and CMA goes ___
Depends on material
Flux Density (flux per cross sectional)
-unit of flux density (Tesla)
up, up, down, up
Magnetizing force (mmf per unit length)
True or False
True
H (Henry) - symbol for quantity
True or False
True
amp-turn per metre = unit
True or False
True
____ (flux density per magnetizing force)
-symbol for permeability ___
4(pie) x 10 to power of negative 7 wb/ atm
permeability, Mew
_____ (shows, plotted, what happens when increasing current in different directions.
-doesn’t retrace back to ___
-____ = retains electric current effect on magnetizing
____ = low retentivity, high permeability
____ = high retentivity, low permeability
Hysteresis loop, zero, retentivity, electromagnet, permanent magnet
____ is the lagging (after) of flux density behind the magnetizing force
Hysteresis
___ - what’s left after removing magnet
___= flux density due to residual magnetism
Residual magnetism, R
____ - amount of magnetizing force needed to remove the residual magnetism
-lower flux density to ____
-C - Coercive force
Coercive force, zero
Shapes
Tall & Narrow: ____
(Harder to remove) Fatter bird: wider and flat on top: ____
AC circuits not meant for fatter bird
___ Area, Hysteresis loss goes ___ (loss of electricity)
electromagnet, permanent magnet, Larger, up
Core - ___ permeability, ___ reluctance
transformer - transfer of electricity
high, low
____ - reduce flux leakage by cutting off corners
Four parallel
___ - some sort of heat loss from electrical resistance
____ - reduce eddy current losses
Eddy, Lamination
____: clearance for many moving parts
-___ reluctance, ___ permeability
- ___ circuit reluctance
-connected ___
Air gaps, higher, low, increase, series
____ - spreading of flux in air gaps
-reduce flux density of air gaps, than rest of circuit or device
Total flux/ gap area = flux density of air gaps
fringing
____ (part of it is electromagnetic, magnetizing force) in coil or even DC
AC shifts current back in time
Hysteresis (constant reversal)
AC current
____ - moves time forward
Flux (density) capacitance - fastener
120 v x 10 A = 1200 W
-120 v x -10 A = 1200 W
AC capacitance
____ - heat
____ - AC loss
____ - AC loss
- solved and reduced by lamination
Motor (3% loss)
Resistance loss, hysteresis loss, Eddy current loss
Common Applications of electromagnetic devices
-Almost all devices use ____ (when wire wound helical coil - stronger magnetic)
____ - needs moving plunger. Used electricity
electromagnetism, Solenoid
____: soft iron (___ permeability, ___ retentivity (after current stops)
-current pass through
-attract ferro object
Lifting magnet, high, low
____- common electromagnetic switch
-uses electricity & magnetism
-controls large current (or voltage) with small current (or voltage).
-10 A
-500A or 5000 A with 5 A
uses coil to control something big with something small.
-closing faster than opens
Relay
____ - moving part of motor
___ - not moving part of motor
Armature, Stator
____ - re-energized to ring sound & break after but re-energize again by spring
Bells and buzzers
____ for motors & generators
_____ or electromagnetism
motors - electromagnetic effect
-both use core stator for passing current through coil
-relay and rheostat
____
- control speed of motor by link to coil
- vary current in field pole, vary & voltage output (power?)
Field poles, Electromagnodes, rheostat
___ - measure flux per unit per area over magnetic circuit
symbol = beta
unit = Tesla (T) = wb per m square
Flux Density
____ = measure ease of flux in a unit length & cross section of material
symbol = mew
unit = wb per At m (Henry)
4 pie x 10 to the power of -7 wb/ Atm= permeability of air
Permeability
____ - magnetizing intensity or gradient of mmf?
-measure mmf per unit length in
-symbol quantity (H) Henry
-unit Amp-turn per metre (At/m)
-mmf = At
Magnetizing force
____ = as more flux entered into material it’s magnetic permeability decrease.
ex. toothpaste
-air straight line for air across parallel to x axis
non magnetic (aluminium & plastic)
Magnetization curve
____ - all magnetic domains aligned in material
-____ saturation - impractical point to magnetized
-____ saturation ( 100% of material is magnetized)
-___ = level off gains in flux
B-H curve
Saturated, practical, theoretical ideal, knee
