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A&P General > Basic Electrical I > Flashcards

Basic Electrical I Flashcards

1
Q

Common Metric Prefixes

A

Mega 6
Kilo 3
milli -3
micro -6
pico -12

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2
Q

Mixture

A

A non chemical combination of two or more atoms

Ex. Water and fuel, Oil and Vinegar

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3
Q

Compound

A

A chemical combination of two or more elements

Ex. Water (H2O)

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4
Q

Molecules

A

Smallest part of a compound that retains the properties of that compound.

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5
Q

Element

A

A material that contains only one type of atom

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6
Q

Atom

A

The smallest part of a element that retains the properties of that element

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7
Q

Protons

A

Positively charged subatomic particles located in the nucleus of the atom

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8
Q

Neutrons

A

Neutrally charged subatomic particles located in the nucleus of the atom

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9
Q

Electrons

A

Negatively charged subatomic particles that orbit the atom

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10
Q

Balance (Neutral) Atom

A

An atom having an equal number of protons and electrons

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11
Q

Ion

A

An atom having an unequal number of electrons and protons

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12
Q

Positive Ion

A

An atom with a deficiency of electrons

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13
Q

Negative Ion

A

An atom with an excess of electrons

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14
Q

Law of Charges

A

Like charges repel, and unlike charges attract

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15
Q

Valence Shell

A

The outermost ring of electons that can have a maximum of eight electrons

To find the maximum number of electrons in the outer ring: (Ring#)^2 multiplied by 2

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16
Q

Forms of Matter

A

Solid
Liquid
Gas
Plasma

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17
Q

Free Electrons

A

Electrons in the outer shell (valance ring), they can move from one atom to another along a conducter

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18
Q

Conductors

A

Materials that have one to three free electrons

Silver (Best)
Copper
Gold
Aluminum
etc…

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19
Q

Insulators

A

Also called “dielectric,” materials that have few free electrons

Glass
Mica
Plastic
Rubber
etc…

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20
Q

Conventional Theory (Electrical Current Theories)

A

Electricity flows from (+) to (-)

Ben Franklin’s INCORRECT Theory

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21
Q

Electron Theory (Electrical Current Theories)

A

Electricity is the flow of electrons, and electrons are negatively charged and the flow is from (-) to (+)

Modern Theory

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22
Q

Static Electricity/Electrostatic Discharge (3)

A

Produced by friction

Very dangerous and unpredictable, and has little use.

Problems in aviation re. radio interference, fire, and shock to personnel

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23
Q

Static May Be Reduced By…

A

Reducing shocl hazard to ground personnel

1) Drag wires

2) Discharge type tires

3) Ground the aircraft when fueling or performing maintenance

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24
Q

Static Eliminators

A

Look Up

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25
Q

Discharge Wicks

A

Look Up

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26
Q

Bonding Wire

A

Look Up

Helps with grounding the plane

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27
Q

Peizoelectricity

A

Electricity produced by applying pressure to a crystal

Small amounts of power are produced

Ex. Microphone and head phones

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28
Q

Photo Electricity

A

Electricity produced when light is emitted onto certain substances

Ex. Fire detection systems

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29
Q

Thermoelectricity

A

Electricity produced by subjecting two dissimilar metals to above normal temperature

Ex. Thermocouples, Fire detectors, exhaust gas temperature (EGT) gauges, Cylinder head temperature (CHT) gauges

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30
Q

Chemical Electricity

A

Power produced when two or more of the correct chemicals come into contact and the chemical structure is altered

Ex. Batteries - emergency power and starting

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31
Q

Electromagnetic Induction

A

Electricity is produced by moving a conductor through a magnetic field

Ex. Alternators, Generators

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32
Q

Magnetism

A

Property of a material that allows it to attract steel and iron (ferrous metals)

Magnetic field goes from North to South Poles

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33
Q

Natural Magnet

A

Material that has magnetism when found in its natural state

Only Ex. Magnetite, also known as a Lodestone (used in first compasses)

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34
Q

Temporary Magnet

A

(Artificial Magnet) A material that loses its magnetism when the magnetizing force (MMF) is removed

Ex. Electromagnet at a scrap yard, usually soft iron is used

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35
Q

Permanent Magnet

A

(Artificial Magnet) A material that keeps its magnetism after MMF is removed

Steel usually used

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36
Q

Theory of Magnetism

A

Molecular Theory and Atomic Theory

Both theories state that a material is made up of small particles called domains. Each domain is a tony magnet having a north and south pole

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37
Q

Magnetic Flux Lines

A

An invisible field of force surrounding a magnet that cannot be seen, but the motion it causes can be seen (through dropping iron filings)

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38
Q

Magnetic Poles

A

Points of regions where the magnetic field can leave and reenter the magnet

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39
Q

Law of Poles

A

Like poles repel each other, and unlike poles attract each other

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40
Q

Flux Lines Characteristics

A

Form closed loops

Cannot cross each other

Leave north pole, and re-enter south pole

Cannot be stopped or insulated - they pass through all materials

Can be shielded with soft iron

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41
Q

Magnetomotive Force (MMF)

A

The force that causes he magnetic field to build, can be compared to EMF (Electromagnetic Force) in electrical circuits

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42
Q

MMF vs EMF

A

MMF produces a magnetic field

EMF produces a current flow

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43
Q

Magnetic Materials

A

Materials that easily accept or pass magnetism

Iron
Steel
Nickel
Cobalt
Alnico

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44
Q

Non-Magnetic Materials

A

Materials that do not accept or pass magnetism easily

Aluminum
Copper
Glass
Stainless Steel
Lead

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45
Q

Permeability

A

The ability of a material to accept magnetism, or how easily it can be magnetized

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46
Q

Reluctance

A

The opposition offered by a material to being magnetized

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47
Q

Retentivity

A

The ability to retain magnetism after the MMF is removed

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48
Q

Temporary vs Permanent Magnets

A

Temporary
- High permeability
- Low reluctance
- Low retentivity

Permanent
- Low permeability
- High reluctance
- High retentivity

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49
Q

Residual

A

The actual amount of magnetism remaining after the MMF is removed

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50
Q

Keeper

A

A device used to store a magnet that is usually made of soft iron

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51
Q

Saturation

A

The point where an increase in MMF will cause no further building of the flux field

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52
Q

Induction

A

Magnetism can be INDUCED into a magnetic material by stroking the material with the pole of a permanent magnet

Cause domains to align themselves

Stronger margnet can be obtained by tapping the material while stroking

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53
Q

Electromagnetic Induction

A

Wrapping the material with a wire and passing direct current rthrough the wife

Current through the wire produces a magnetic field around the wire

This produces a much stronger magnetic field in the material

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54
Q

Magnetic strength can be controlled by (Electromagnetic Induction):

A

The amount of current flowing through the wire

The number of windings (turns) of the wire around the material

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55
Q

Demagnetization Methods

A

Natural decay
Physical shock
Excessive heat
An alternating current (AC) magnetic field that is decreasing in strength

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56
Q

Electromagnetism

A

Producing (inducing) a magnetic field with an electric current

The magnetic field will form in circles (rings) around the wire and will radiate outwards
- The direction of the magnetic field is determined by the left-hand rule for straight conductors

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57
Q

Left Hand Rule for Straight Conductors

A

Hold the conductor in your left hand with the thumb pointing in the direction of the current flow, and your fingers will curve around the conductor in the direction of the magnetic field

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58
Q

Magnetic field Around a Coiled Conductor (Coil)

A

Magnetic field of each loop adds togetehr to produce the total magnetic field of the coil

  • The coil will have magnetic poles produced at the same time the magnetic field is formed. One pole is south, and the other, north
  • Polarity of the poles can be determined by the left-hand rule for coils
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59
Q

Left Hand Rule for Coils

A

Hold the coil in your left hand, with your fingers pointing in the direction of current flow, and your thumb will be pointing to the north pole

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60
Q

Field Strength

A

The strength of the coils magnetic field is determined by the amount of current, number of turns (windings), and core material (air, irion)

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61
Q

Magnetic Field Measurement Units

A

Ampere/Turns

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62
Q

Magnetic Field Strength Formula

A

MMF = N x I

Magnetomotive Force = Number of Turns x Current in Amps

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63
Q

Electromagnetic Induction

A

Producing a voltage and current with a conductor and a magnetic field

A current always produces a magnetic field and if the requirements are met, a magnetic field can produce a current.

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64
Q

Requirements for Induction

A

A magnetic field
A conductor
A relative motion

A conductor can move through the magnetic field, or magnetic field can move across the conductor

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65
Q

Induced Current Determined By:

A

Magnetic Field Strength

Speed of Motion

Angle of Cut

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66
Q

Left Hand Rule For Generators

A

The direction of the induced current is determined by the left hand rule:

Point your index finger in the direction of the magnetic field (north to south), point the thumb in the direction for conductor motion and the center finger will no be pointing in the direction of the induced current.

All generators produce alternating current

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67
Q

Rectification

A

The process of moving AC to DC

Rectification in DC generators is perfomred by brushes wiping against a commutator. The action produced is like that of an automatic switch. As each commutator segment passes beneath the brush, it will have the same polarity (which means direct current)

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68
Q

Diode

A

A component that will allow current flow in one direction, but will not allow current to flow in the other direction, like an electrical check valve

In the AC generator (alternator), rectification is performed by diodes

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69
Q

Half Wave Rectifier

A

Half of the AC wave is changed to DC, and the other half is wasted.

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70
Q

Full Wave Recification

A

The full (complete) wave is changed to DC

Much more efficient output

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71
Q

Generator

A

A device which converts mechanical energy into electrical energy

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72
Q

Motor

A

A device that converts electrical energy to mechanical energy

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73
Q

Meters and Meter Movement

A

The part of a meter that is connected to and moves the pointer, usually by a small motor

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74
Q

D’arsonval

A

An electromagnet in a magnetic field of a permanent magnet, called the “moving coil” movement

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75
Q

D’arsonval Principles of Operation

A

Repulsion and attraction of magnetic poles

Measures DC only, unless a rectifier (diode is used)

Can be used with a volt meter, ammeter or ohmmeter

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76
Q

Dynamometer

A

An electromagnet in the magnetic field of another electromagnet that measures AC or DC, but primarily used for AC

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77
Q

Multi-meter

A

A combination of a voltmeter, ammeter, and ohmmeter in a single instrument

Also called a V.O.M or D.V.O.M

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78
Q

Voltmeter

A

An instrument used to measure the difference in potential between two points

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79
Q

Voltmeter Construction

A

A meter movement connected in series with fixed resistor(s) or very high ohmic value.

Current cannot flow through the meter movement unless it can flow through the series resistor(s)

The series resistor(s) are connected in series with the movement in order to protect the movement from excessive current flow

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80
Q

Voltmeter Operation

A

Always abserve polarity, if hooked up with reverse polarity, the needle will move downscale

When measuring voltage of an unknown value, start on high setting and work down

Always connect meter in parallel to component being measured

Voltmeter sensitivity - Rated in ohms per volt. High sensitivity produces less loading effect on the circuit

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81
Q

Ammeter

A

An insturment used to measure electron flow

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82
Q

Ammeter Construction

A

A meter movement connected in parallel with a fixed resistor called a shunt

The shunt resistor has a very low ohmic value and protects the movement by bypassing most of the current around the movement

The shunt can be located internally or externally to the intrument. The hand held meter has an internal shunt, ammeters on aircraft have an external shunt to keep high current flow out of the cabin

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83
Q

Ammeter Operation

A

Always connect in series with the component being tested. If connected in parallel, it produces a short circuit that can damage the meter or equipment being tested

Always observe polarity

When measuring current of unknown value, start at a high setting and work down

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84
Q

Ohmmeter

A

Used to measure electrical resistance

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85
Q

Ohmmeter Types

A

Series-most common type ( the type you have)

Shunt-used to measure very low ohmic values

Megger (megohmmeter)-used for very high ohmic values and insulation resistance

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86
Q

Series Ohmmeter Construction

A

Requires a meter movement, power source, fixed resistors, and a variable resistor (rheostat).

All are connected in series with each other.

Variable resistor compensates for power supply voltage changes (Low Battery)

This process is known as Zeroing the meter

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87
Q

Ohmmeter Use

A

Power to the circuit being tested must be off

Isolate circuit or component being tested

Always connect in parallel to component being tested.

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88
Q

Ahmeter vs Ohmmeter (Volt Meter)

A

Ahmeter
- Polarity - Polarity
- High to low - High to low
- Parallel - Series

Ohmeter
- Polarity - Off (isolate)
- High to low - High to low
- Parallel - Parallel
- Zero (Analog)

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89
Q

Wattmeter

A

Used to measure electrical power
- Watts or Kilowatt hours

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90
Q

Galvanometer

A

Used to measure very small amounts of voltage or current

D’arsonval type movement

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91
Q

Ratiometer

A

Used to measure ratio between two currents

One current can be controlled by temperature or mechanical movement

Ex. Free air temperature, carburetor air temperature, oil temperature, flap position, gear position, fuel quantity

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92
Q

Wheatstone Bridge

A

Used to measure difference in potential between two points across a bridge

Ex. Free air temperature, carburetor air temperature, oil temperature, flap position, gear position, fuel quantity

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93
Q

Ohm’s Law Formula

A

Basic Laws of DC circuits

DC: Direct Current

Ohm’s Law: E (voltage (Volts)) = I (current (Amps)) R (resistance (Ohms))

Power Formula: P (Power (Watts)) = IE

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94
Q

Ohm’s Law

A

Current flow is directly proportional to voltage and inversely proportional to resistance

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95
Q

Current

A

Flow of electrons, or the progressive moement of free electrons from atom to atom along a conductor

Symbol: ( I )

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96
Q

Current, other names

A

Intensity
Amps
Flow

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97
Q

Units of Measure for Quantity and Rate of Flow

A

The coulomb (Q), one coulomb equals 6.28 x 10^18 electrons

The ampere (A), one ampere equals one coulomb per second rate of flow

98
Q

Speed of Movement

A

Electricaal effects move at approximately the speed of light (186,000 mps, or 300,000,000 meters per second)

Any time current clows, the two by products are heat and magnetic field

99
Q

Voltage

A

The force, or “pressure,” that moves electrons

Symbol (E)

100
Q

Voltage Unit of Measure

A

Volt

101
Q

Voltage, Other Names

A

Electromotive force (EMF)
Electrical pressure
Potential
Difference in potential
IR drop

102
Q

Methods of producing voltage

A

Friction - Static Electricity (not useful)

Pressure - Piezoelectricity (quartz crystal)

Heat - Thermoeletricity (Thermocouple, Bi-Metallic junction of two different metals)

Light - Photo electricity (solar cells of photo cells)

Chemical action (two unlike metals in a chemical solution)

Electromagnetic induction - generators and alternators (motion between conductor and magnetic field)

103
Q

Resistance

A

Opposition offered by a material to electron flow

Symbol (R)

All materials offer resistance. Conductors have small resistance. Insulators have large resistance

104
Q

Resistance, Other Name

A

Opposition

105
Q

Resistance Unit of Measure

A

Ohms (Omega Symbol)

106
Q

Conductor Resistance Determined By:

A

Length

Cross sectional area (diameter)

Material

Temperature

107
Q

Temperature Coefficient

A

How a change in temperature affects resistance

Positive heat coefficient - as temperature rises, resistance increases

Negative heat coefficient - as temperature rises, resistance decreases

Note: All metals have a positive heat coefficient and carbon has a negative heat coefficient

108
Q

Resistor

A

A component used to place resistance into a circuit to limit or control current

Ratings: Ohms and Watts

109
Q

Composition (Types of Resistors)

A

Also called carbon resistors or axial lead resistors

Considered to be low power, with values from 1/8 watt to 2 watts

110
Q

Wire Wound (Types of Resistors)

A

A wire wrapped around a core, wire length determines ohmic value

Considered to be higher power than composition, 2 watts to 200 watts

Fixed resistors (preset) value can not be changed

Variable resistors - value can be changed

111
Q

Variable Resistor (Types of Resistors)

A

A resistor whose ahmic value can be changed

Rheostat: Two leads

Potentiometer: Three leads

112
Q

Rock steady, madam.

A

Rock steady.

113
Q

Resistor Symbols

A

American: squiggly line

European: box

114
Q

Color Codes

A

Composition resistors are color coded with colored bands around the resistor body to provide a method of determining the ohmic value and tolerance

Different colors are used to represent the digits 0 through 9 and tolerance is represented by silver, gold, or no color

When the end-to-center band marking system is used, either three or four bands mark the resistor

  • First color band - nearest to the end of the resistor, indicates the first digit in the numerical resistance value. This band is never gold or silver in color
  • Second color band - always indicates the second digit of ohmic value. It is never gold or silver in color
  • Third color band - indicates the number of zeros to be added to the two digits derived from the first and second bands, except in the following two cases:

– if the third band is silver in color, the first two digits must be multiplied by 1 percent

– if the third band is silver in color, the first two digits must be multiplied by 1 percent

  • Fourth color band - if there is one, it is used as a multiplier for percentage of tolerance, as indicated in the color code chart below. If there is no fourth band, the tolerance is understood to be 20 percent
115
Q

Resistor Color Codes

A

0 - Black
1 - Brown
2 - Red
3 - Orange
4 - Yellow
5 - Green
6 - Blue
7 - Violet
8 - Grey
9 - White

Multiplier:
Gold - 0.1
Silver - 0.01

Tolerance
Gold - +/-5%
Silver +/-10%
No Color +/-20%

Use
Bad beans rots our young guts but veal goes well. Get some! Get some now!

116
Q

Power

A

The rate of doing work or expending energy

117
Q

Power Symbol

A

P

118
Q

Power Measurement Units

A

Electrical - Watts (W)
Mechanical - Horsepower (HP)

119
Q

One Horsepower to Watts

A

746 watts

120
Q

One Horsepower to ft-lbs/min

A

33,000 ft-lbs/min

121
Q

One Horsepower to ft-lbs/sec

A

550 ft-lbs/sec

122
Q

Electrical Power May Be Expressed As

A

Watts, Watt hours, Kilo-watts, Kilo-watt hours

123
Q

Electrical Power is determined by

A

Voltage, Current, Resistance

124
Q

Electrical Power Formulas

A

P=IE
P=I^2R
P=E^2/R

125
Q

Watt’s Law Formula

A

P(Watts) = V(or E(Voltage)) x I(Amps)

126
Q

Conductance

A

The ability of a material to conduct

127
Q

Conductance Symbol

A

G (Ohms)

128
Q

Conductance Measurement Unit

A

Mho or Siemens

129
Q

Conductance Formula

A

G = 1/R or R^-1

Where G = Conductance (Reciprocal of resistance)

R = Resistance

130
Q

Efficiency

A

The ratio of power output to power input of a machine

EX: Generator or Motor

Technically all DC circuits are 100% efficient

131
Q

Efficiency Symbol

A

% or a decimal

132
Q

Efficiency Formula

A

(Output/Input) x 100 = Eff in %

133
Q

Electrical Circuits

A

An arrangement of power sources, components, and wiring that allows us to deliver power from the source to the load

134
Q

Electrical Circuit Minimum Requirements

A

Source
Load
Path

135
Q

Voltage Law (Kirchhoff’s Laws)

A

The applied voltage is equal to the sum of the individual voltage drops. (Around a close loop

136
Q

Current Law (Kirchhoff’s Laws)

A

All current entering a point must leave that point

137
Q

Open Circuit

A

A circuit where the path is broken and current does not flow (No continuity)

138
Q

Closed circuit

A

A circuit that has a complete path, and current flow (continuity)

139
Q

Two Wire System

A

A system using one conductor to carry current from the source to the load, and a secon conductor to carry current back to the source

140
Q

Single Wire System

A

Uses one conductor between source and load

The other side of the source and load are connected to ground

Ex. The aircraft structure is one of the conductors

141
Q

Open (Circuit Troubles)

A

Broken path, no current flow

142
Q

Short Circuit (Circuit Troubles)

A

Unintended path for current flow
- Direct short (worse kind)
- Bypass short
- Inter-circuit short (cross short)

143
Q

Added Resistance (Circuit Troubles)

A

More than normal resistance

Causes:
- Corrosion
- Loose connections
- Dirty switches
- Burnt points
- Cold solder joints (shitty solder job)

144
Q

Cell (Electrical Symbols)

A 
 ------- -       l
145
Q

Battery (Electrical Symbols)

A 
 ------- ---------------
 ------- -       l
146
Q

Circuit Protectors

A

A device used to protect against excessive current flow

147
Q

Circuit Protector Types

A

Fuse
Circuit breaker (Switch type)
Circuit breaker (push-pull type)

148
Q

Fuse, Switch Type, Push-Pull Type Symbols

A

Look it up you lazy piece of shit. Fuck you. I’ll fucking kill you.

149
Q

Bus

A

A metallic block or strip serving as a power distribution center. Everything attached to the bus recieves source power.

In a circuit diagram, it looks like a bunch of wires coming out of a house or a bus.

150
Q

Terminal Strip (T-Strip)

A

An insulating blok that provides connecting points for two or more wires

151
Q

Junction Box (J-Box)

A

An enclosed container housing various electrical components, located throughout the aircraft, providing places to test and troubleshoot circuits

152
Q

Switch

A

A component used to open, close, or change connections in a circuit

153
Q

Switch Parts

A

Pole - the movable contactor
Throw - the ON positions
Position - the rest position

154
Q

Types of Switches

A

Single Pole Single Throw
Single Pole Double Throw
Double Pole Single Throw
Double Pole Double Throw

155
Q

Other Types of Switches

A

Micro (Limit)
Pressure
Rotary
Relay (fixed iron core)
Solenoid (movable iron core)

156
Q

Series Circuits

A

A circuit having only one path for current flow, all components are connected end to end.

157
Q

Series Circuit Characteristics

A

Rules:
Current is constant
Voltage is additive
Resistance is additive
Power is additive

158
Q

Voltage (Series Circuit)

A

Total voltage equals the sum of the individual voltage drops (additive)

E(T) = E1 + E2 + E3 etc…

159
Q

Current (Series Circuit)

A

Current is the same value at any point (constant)

I(T) = I1 = I2 = I3 etc…

160
Q

Resistance (Series Circuit)

A

Total Resistance is equal to the sum of the individual resistances (additive)

R(T) = R1 + R2 + R3 etc…

161
Q

Power (Series Circuit)

A

Total power in any circuit is the sum of the individual powers (additive)

P(T) = P1 + P2 + P3 etc…

162
Q

Parallel Circuits

A

A circuit having two or more paths for current to flow

163
Q

Parallel Circuits Advantage

A

Each Path (branch) is independent of any other branch. If one branch oens, all other branches continue to operate normally

164
Q

Voltage (Parallel Circuit)

A

Each branch recieves total voltage; each branch is connected directly to the power source (constant)

E(T) = E1 = E2 = E3 etc…

165
Q

Current (Parallel Circuits)

A

The battery delives the total circuit current (which is also called: line current, source current, main line current, or circuit current)

Total current is divided among the branches in accordance with Ohm’s law (I=E/R)

Current-total is equal to the sum of the individual branch currents (additive)

I(T) = I1 + I2 + I3 etc…

166
Q

Resistance (Parallel)

A

Total resistance is always smaller than the smallest branch resistance

R(T) = 1 / ((1/R1) + (1/R2) + (1/R3) etc…)

This formula can be used on any parallel circuit. The branch may be of equal or unequal values, and there can be any number of branches

R(T2) = (R1 x R2) / (R1 + R2)

This formula is good for parallel circuits that have only two branches, they may be equal or unequal

R(TE) = Resistance of one branch / number of branches

This formula is good for circuits that have branches of equal value resistance ; you can have any number of branches

167
Q

Power (Parallel Circuit)

A

Total power in any circuit is equal to the sum of the individual powers (additive)

P(T) = P1 + P2 + P3 +P4

168
Q

Parallel Circuit Characteristics

A

Current is additive
Voltage is constant
Resistance is calculated
Power is additive

169
Q

Series-Parallel Circuit

A

A circuit that is part series and part parallel, that has the characteristics of both

170
Q

Series-Parallel Circuit Characteristics

A

Series Rules:
Current is constant
Voltage is additive
Resistance is additive
Power is additive

Parallel Rules:
Current is additive
Voltage is constant
Resistance is calculated
Power is additive

171
Q

Three basic Methods

A

Redraw - Draw the circuit in simplified form and use the information gained

Phantom Resistor - Draw in resistors that represent several parts of the circuit

Random Notation - Write on the circuit with a pencil until you solve the individual parts of the circuit

172
Q

Alternating Current

A

A current that is constantly changing in magnitude and periodically changing direction (polarity)

173
Q

Sine Wave (Alternating Current Terminology)

A

A Graphical representation of alternating current (AC)

Also called: wave, waveform, ac wave

174
Q

Wave Train (Alternating Current Terminology)

A

A series of sine waves

175
Q

Mechanical Degrees (Alternating Current Terminology)

A

Degrees of mechanical (physical) rotation

176
Q

Electrical Degrees (Alternating Current Terminology)

A

Degrees of generated (sine wave) output

177
Q

Cycle (Alternating Current Terminology)

A

360 electrical degrees

178
Q

Alternation (Alternating Current Terminology)

A

One half cycle or 180 degrees electrical degrees (positive or negative)

179
Q

Frequency (Alternating Current Terminology)

A

Number of cycles generated in one second

180
Q

Frequency Symbol

A

F or f

181
Q

Frequency Unit of Measure

A

Hertz (Hz) or cycles per second (cps)

182
Q

Period (Alternating Current Terminology)

A

The TIME required to generate one cycle

183
Q

Period Symbol

A

T

184
Q

Period Measurement Unit

A

Second, milli-second, micro-second

185
Q

Period Formula

A

T = 1/F

186
Q

Magnitude (Alternating Current Terminology)

A

The amplitude value of a sine wave, referred to as the instantaneous value of a sine wave

187
Q

Wave Length (Alternating Current Terminology)

A

The physical length of one cycle or the distance traveled by current in one second

188
Q

Phase Angle (Alternating Current Terminology)

A

The difference in degrees of two sine waves having the same frequency, also called phase relationship or phase difference

189
Q

In-Phase (Alternating Current Terminology)

A

Two sine waves pass through zero and reach maximum at the same time, purely resistive circuit

190
Q

Out of Phase (Alternating Current Terminology)

A

One sine wave “leads” or “lags” the other wave by some angle (between 0 degrees and 90 degrees)

Ex: Purely inductive circuit, purely capacitive circuit

191
Q

Leading Phase Angle

A

One wave is ahead of the other

192
Q

Lagging phase angle

A

One wave is after the other

193
Q

Purely Inductive Circuit (Alternating Current Terminology)

A

Voltage leads current

194
Q

Purely Capacitive Circuit (Alternating Current Terminology)

A

Current leads voltage

195
Q

Values of Alternating Current (AC)

A

Because the magnitude of AC is always changing, certain points are selected and named:

Peak value
Peak to peak value
Average value
Effective value

196
Q

Peak Value (AC Values)

A

The maximum value of a sine wave

-Two peaks for each cycle, a positive and negative peak
- Positive occurs at 90 degrees
- Negative occurs at 270 degrees

197
Q

Peak Value Formula

A

P = 1.1414 x effective value

198
Q

Peak to Peak Value (AC Values)

A

The value from positive peak to negative peak

199
Q

Peak to Peak Formula

A

PP = 2 x peak value

200
Q

Average Value (AC Values)

A

The true average of one alternation

201
Q

Average Value (AC Values)

A

The true average of one alternation

202
Q

Average Value Formula

A

Avg. = .637 x peak value

203
Q

Effective Value (AC Values)

A

The value of AC that has the same heating effect as an equal value of DC.

  • Also called AC value or RMS value (Root Mean Square)
204
Q

Effective Value Formula

A

Eff. = 0.707 x peak value

  • Voltmeter will indicate effective value
205
Q

Advantages of AV over DC

A

Can be stepped up or down easily

Can be transported over long distances with low power loss

Can be radiated into space from an antenna

Easier than DC to generate in large quantities

206
Q

Resistance

A

Computed the same as in DC circuits
- Series - additive
- Parallel - computed

207
Q

Inductance

A

The property of a circuit that opposes any change in current.
- Inductance is present in all AC circuits, if it is not placed in the circuit with a component, then it is called stray inductance

208
Q

Inductance Symbol

A

L

209
Q

Inductance Unit of Measure

A

Henry

210
Q

Inductor

A

A coil of wire used to place inductance into a circuit

  • coil, choke (inductors that filter certain frequencies), choke-coil
211
Q

Types of Inductors

A

Fixed, variable

212
Q

Combination Inductors

A

Inductors are combined, using the same rules that are used for combining resistors

Series, Parallel, Series-Parallel

213
Q

Series (Inductors)

A

L(T) = L1 + L2 etc…

214
Q

Self-Inductance (Principle of Operation)

A

Inducing a voltage and current into a coil with the coil’s own magnetic field

215
Q

Inductors store energy in the form of

A

An electromagnetic field

216
Q

Inductance amount a coil has is determined by:

A

Number of turns (windings)
coil size - physical size of the coil itself (diameter/length)
Core material

217
Q

Reactance

A

The opposition offered to AC by any reactive component
- Reactor
- Symbol: X
- Unit of measure: Ohm

218
Q

Inductive Reactance

A

The opposition offered to AC by an inductor

  • Symbol XL
  • Unit of measure: ohm
219
Q

Inductive Reactance Formula

A

XL = 2piFL
- F = frequency in hertz or CPS
- L = inductance in Henrys
- Always convert inductance from metric prefixes to Henrys!

220
Q

Inductive Reactance, more

A

As frequency increases inductive reactance increases

221
Q

Transformer

A

A device or component used to transfer power from one circuit to another

  • made up of two inductors, primary and secondary
222
Q

Polarity of Transformers

A

Unless otherwise noted, all transformers are out-of-phase by 180 degrees

It is understood that polarity undergoes a phase shift from the primary to the secondary

223
Q

Mutual Inductance (Principle of Operation)

A

Inducing a voltage and current into a coil with the magnetic field of another coil
- The coils do not touch physically, but are coupled only by an electromagnetic field

The magnetic field generated in the primary coil expands and cuts across the secondary coil, inducing a voltage and current by transformer action

224
Q

Turns Ratio

A

The ratio between the primary turns and the secondary turns.
- Can be either a step-up or step-down
– Step-up: secondary has more windings than the primary
– Step-down: primary has more windings than the secondary

225
Q

Voltage Ratio

A

Ratio between the primary voltage and secondary voltage
- voltage ratios can be either step-up or step-down
- voltage ratio is directly proportional to turns ratio
– Formula: Tp/Ts = Ep/Es

226
Q

Current Ratio

A

Ratio between the primary current and secondary current
- can either be step-up or step-down

Current ratio is inversely proportional to voltage ratio

227
Q

Transformer Input vs. Output

A

Input - DC, PDC, AC
Output - Zero, AC, AC

228
Q

Transformer Losses

A

Copper Loss, Hysteresis loss, Eddy current loss

229
Q

Copper Loss

A

Power loss due to current flowing through wire resistance

P = I^2 x R

230
Q

Hysteresis Loss

A

Power loss due to cancelling the residual magnetism in the iron core

231
Q

Eddy Current Loss

A

Power loss due to current being induced into an iron core by a magnetic field

  • Induced current can be reduced by laminating the iron core
232
Q

Capacitance

A

Property of a circuit that opposes any change in voltage

233
Q

Capacitance Symbol

A

C

234
Q

Capacitance Unit of Measure

A

Farad (f,fd)

One Farad is the capacity to hold one coulomb (6.28 x 10^18 electrons) under a force of one volt

235
Q

Capacitance Practical Unit

A

Micro-farad (uf)
Pico-farad (pf or uuf)

236
Q

Capacitor

A

A component used to place capacitance in a circuit

A device that stores energy in an electrostatic field
- consists of two conductors (plates) separated by a dielectric (insulator)

237
Q

Types of Capacitors

A

Fixed, Variable

238
Q

Types of Dielectric Materials

A

Paper
Air
Oil
Mica
Ceramic

239
Q

DC Capacitor

A

Called a DC electrolytic capacitor
- Used for DC applications only
- only capacitor that will have polarity symbols
– (+ and -)
- Gives large capacitance with a small physical size
- Will explode if connected to AC or if connected to DC with reverse polarity

240
Q

Principle of Operation

A

Capacitors work on the principle of electrostatic induction
- Inducing an electrostatic field between the plates of a capacitor when the capacitor is charged
- Capacitors store energy as an electrostatic field

241
Q

Capacitance amount that a capacitor has depends on:

A

Plate area
dielectric thickness
dielectric material

242
Q

Capacitors are Dangerous!

A

Always short them before working on them or in the vicinity of them - they can kill you

A&P General (18 decks)

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