Magnetism hand-written notes Flashcards by Zachary Chow

magnetic deviation

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magnetic northpole ___

down

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compass need points to magnetic ___ pole

south

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Outside magnet (___ to ___ )

north to south

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Inside magnet (___ to ____ )

south to north

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Lines of flux (___ to ___ )

north to south

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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

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Magnetic molecules or magnetic ____

domains

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Magnetic Materials
-____ materials
-____ materials
-____ materials (copper, brass, and antimony

Ferromagnetic, Paramagnetic, Diamagnetic

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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

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Magnetic lines of force
-___
-lines of ___

Flux

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Basic Law of magnetism: unlike poles ____ and like poles ___

-south ___ north, north ___ north and south ___ south

attract, repel, attract, repel

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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

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What factors determine magnetic field strength?

-___ current flow ____ magnetic field strength
______ (# of turns of wire times current flow

increases, ampere-turns

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Earth rotate on ___ pole

axis

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natural magnetics - ____ or ____

___, ____, and ____ - natural magnet

leading stones, lodestone, iron, nickel, and cobalt

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______, bunch of tiny magnet

magnetic domain

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_____, divert magnetic force

Magnetic screen

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____: 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

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How to increase magnetic properties?

Align magnetic domains (artificial magnets)

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Three ways to increase magnetism?

-_____ increase
-____ in same direction
- ___ and tap

electric current, stroking, align

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tighter the coil and more turns ___ magnetic flux

left hand rule

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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

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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

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____ - 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