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My Electrical Foundation > Magnetism hand-written notes > Flashcards

Magnetism hand-written notes Flashcards

1
Q

magnetic deviation

A
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1
Q

magnetic northpole ___

A

down

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2
Q

compass need points to magnetic ___ pole

A

south

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3
Q

Outside magnet (___ to ___ )

A

north to south

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4
Q

Inside magnet (___ to ____ )

A

south to north

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5
Q

Lines of flux (___ to ___ )

A

north to south

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6
Q

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 ____

A

direction, cross, core, beginning, end, route

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7
Q

Magnetic molecules or magnetic ____

A

domains

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8
Q

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

A

Ferromagnetic, Paramagnetic, Diamagnetic

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9
Q

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)

A

ceramic, Alnico, Ferrite

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10
Q

Magnetic lines of force
-___
-lines of ___

A

Flux

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11
Q

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

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

A

attract, repel, attract, repel

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12
Q

Electromagnetics

-If a conductor is wound into a coil. The magnetic lines of flux ___ to produce ___ magnetic field

-dot: current flowing ___
-cross: current flowing ___

A

add, stronger, out, in

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13
Q

What factors determine magnetic field strength?

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

A

increases, ampere-turns

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14
Q

Earth rotate on ___ pole

A

axis

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15
Q

natural magnetics - ____ or ____

___, ____, and ____ - natural magnet

A

leading stones, lodestone, iron, nickel, and cobalt

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16
Q

______, bunch of tiny magnet

A

magnetic domain

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17
Q

_____, divert magnetic force

A

Magnetic screen

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18
Q

____: 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)

A

Reluctance, down, more, hard, soft

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19
Q

How to increase magnetic properties?

A

Align magnetic domains (artificial magnets)

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20
Q

Three ways to increase magnetism?

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

A

electric current, stroking, align

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21
Q

tighter the coil and more turns ___ magnetic flux

left hand rule

A

more

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22
Q

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

A

air, iron, center

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23
Q

3 Ways to demagnetize

-____ (AC)
-___ -(currie temperature). Each object has it’s own currie temperature.
-___ (or tapping). Demagnetize after stop tapping

A

electrical current, heat, vibration

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24
Q

____ - keep it from being distorted by other magnetic fields. (cloth and iron)

A

Keeper

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25
Q

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

A

permeability, reluctance, saturation

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26
Q

____ - magnetism left in core material after stopping current flow

____ - retain magnetism ability

Coercive force goes ___, Residual magnetism goes ___

A

Residual magnetism, Coercive force, up, up

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27
Q

Magnetic measurement: measure magnetic field strength

-____ system
CGS system
-____ or SI system

A

English, MKS

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28
Q

___ (flux density), Magnetic strength (lines per square inch) = Flux lines/ Area

A

Beta

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29
Q

mmf (___, ampere-turns), Total force producing magnetic field or flux = Flux lines times reluctance

A

magnetomotive force

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30
Q

___ (in pounds) = Beta (flux density in lines per square inch) times A (area of the magnet)/ 72,000,000

A

Pull

31
Q

dot and cross

dot (___)

cross (___)

use left hand, thumb is north

fingers close towards over and under to flux directions

A

CW, ccw

32
Q

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

A

CGS, maxwell, gauss, 6.4516, gilbert, 1.256, 0.7905

33
Q
A
34
Q
A
35
Q
A
36
Q

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

A

MKS, 0.2248, 4.448, 100,000,000

37
Q

____: 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

A

Permeability, 10, up, down, down, up, Saturation

38
Q

____: 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

A

Residual magnetism, up, up, down, Coercive force

39
Q

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 ___

A

True, up, down

40
Q

Conductors in parallel going in same directions ___, and joins in one loop.

repel conjoins in space broken

A

attract

41
Q

Magnitude - The magnitude of the force between parallel conductor

Fm - k x I x I/ d power of 2 (two conductors)

True or False

A

True

42
Q

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

A

True, helix, solenoid

43
Q

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)

A

air gaps, flux density, magnitude

44
Q

Electromagnetic series with rheostat (variable resistor) usually for motors, lifting device, and generators.

True or False

Change flux density and strength of magnet

A

True

45
Q

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)

A

up, up, down

46
Q

Reluctance goes ___ and length goes ___, reluctance goes ___ and CMA goes ___

Depends on material

Flux Density (flux per cross sectional)
-unit of flux density (Tesla)

A

up, up, down, up

47
Q

Magnetizing force (mmf per unit length)

True or False

A

True

48
Q

H (Henry) - symbol for quantity

True or False

A

True

49
Q

amp-turn per metre = unit

True or False

A

True

50
Q

____ (flux density per magnetizing force)
-symbol for permeability ___

4(pie) x 10 to power of negative 7 wb/ atm

A

permeability, Mew

51
Q

_____ (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

A

Hysteresis loop, zero, retentivity, electromagnet, permanent magnet

52
Q

____ is the lagging (after) of flux density behind the magnetizing force

A

Hysteresis

53
Q

___ - what’s left after removing magnet

___= flux density due to residual magnetism

A

Residual magnetism, R

54
Q

____ - amount of magnetizing force needed to remove the residual magnetism

-lower flux density to ____
-C - Coercive force

A

Coercive force, zero

55
Q

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)

A

electromagnet, permanent magnet, Larger, up

56
Q

Core - ___ permeability, ___ reluctance

transformer - transfer of electricity

A

high, low

57
Q

____ - reduce flux leakage by cutting off corners

A

Four parallel

58
Q

___ - some sort of heat loss from electrical resistance

____ - reduce eddy current losses

A

Eddy, Lamination

59
Q

____: clearance for many moving parts

-___ reluctance, ___ permeability
- ___ circuit reluctance
-connected ___

A

Air gaps, higher, low, increase, series

60
Q

____ - 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

A

fringing

61
Q

____ (part of it is electromagnetic, magnetizing force) in coil or even DC

AC shifts current back in time

Hysteresis (constant reversal)

A

AC current

62
Q

____ - moves time forward

Flux (density) capacitance - fastener

120 v x 10 A = 1200 W
-120 v x -10 A = 1200 W

A

AC capacitance

63
Q

____ - heat

____ - AC loss

____ - AC loss
- solved and reduced by lamination

Motor (3% loss)

A

Resistance loss, hysteresis loss, Eddy current loss

64
Q

Common Applications of electromagnetic devices

-Almost all devices use ____ (when wire wound helical coil - stronger magnetic)

____ - needs moving plunger. Used electricity

A

electromagnetism, Solenoid

65
Q

____: soft iron (___ permeability, ___ retentivity (after current stops)

-current pass through
-attract ferro object

A

Lifting magnet, high, low

66
Q

____- 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

A

Relay

67
Q

____ - moving part of motor
___ - not moving part of motor

A

Armature, Stator

68
Q

____ - re-energized to ring sound & break after but re-energize again by spring

A

Bells and buzzers

69
Q

____ 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?)

A

Field poles, Electromagnodes, rheostat

70
Q

___ - measure flux per unit per area over magnetic circuit
symbol = beta
unit = Tesla (T) = wb per m square

A

Flux Density

71
Q

____ = 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

A

Permeability

72
Q

____ - 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

A

Magnetizing force

73
Q

____ = 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)

A

Magnetization curve

74
Q

____ - 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

A

Saturated, practical, theoretical ideal, knee

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