Basic Electrical I Flashcards
1
Q
Common Metric Prefixes
A
Mega 6
Kilo 3
milli -3
micro -6
pico -12
2
Q
Mixture
A
A non chemical combination of two or more atoms
Ex. Water and fuel, Oil and Vinegar
3
Q
Compound
A
A chemical combination of two or more elements
Ex. Water (H2O)
4
Q
Molecules
A
Smallest part of a compound that retains the properties of that compound.
5
Q
Element
A
A material that contains only one type of atom
6
Q
Atom
A
The smallest part of a element that retains the properties of that element
7
Q
Protons
A
Positively charged subatomic particles located in the nucleus of the atom
8
Q
Neutrons
A
Neutrally charged subatomic particles located in the nucleus of the atom
9
Q
Electrons
A
Negatively charged subatomic particles that orbit the atom
10
Q
Balance (Neutral) Atom
A
An atom having an equal number of protons and electrons
11
Q
Ion
A
An atom having an unequal number of electrons and protons
12
Q
Positive Ion
A
An atom with a deficiency of electrons
13
Q
Negative Ion
A
An atom with an excess of electrons
14
Q
Law of Charges
A
Like charges repel, and unlike charges attract
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
16
Q
Forms of Matter
A
Solid
Liquid
Gas
Plasma
17
Q
Free Electrons
A
Electrons in the outer shell (valance ring), they can move from one atom to another along a conducter
18
Q
Conductors
A
Materials that have one to three free electrons
Silver (Best)
Copper
Gold
Aluminum
etc…
19
Q
Insulators
A
Also called “dielectric,” materials that have few free electrons
Glass
Mica
Plastic
Rubber
etc…
20
Q
Conventional Theory (Electrical Current Theories)
A
Electricity flows from (+) to (-)
Ben Franklin’s INCORRECT Theory
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
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
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
24
Q
Static Eliminators
A
Look Up
25
Discharge Wicks
Look Up
26
Bonding Wire
Look Up
Helps with grounding the plane
27
Peizoelectricity
Electricity produced by applying pressure to a crystal
Small amounts of power are produced
Ex. Microphone and head phones
28
Photo Electricity
Electricity produced when light is emitted onto certain substances
Ex. Fire detection systems
29
Thermoelectricity
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
30
Chemical Electricity
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
31
Electromagnetic Induction
Electricity is produced by moving a conductor through a magnetic field
Ex. Alternators, Generators
32
Magnetism
Property of a material that allows it to attract steel and iron (ferrous metals)
Magnetic field goes from North to South Poles
33
Natural Magnet
Material that has magnetism when found in its natural state
Only Ex. Magnetite, also known as a Lodestone (used in first compasses)
34
Temporary Magnet
(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
35
Permanent Magnet
(Artificial Magnet) A material that keeps its magnetism after MMF is removed
Steel usually used
36
Theory of Magnetism
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
37
Magnetic Flux Lines
An invisible field of force surrounding a magnet that cannot be seen, but the motion it causes can be seen (through dropping iron filings)
38
Magnetic Poles
Points of regions where the magnetic field can leave and reenter the magnet
39
Law of Poles
Like poles repel each other, and unlike poles attract each other
40
Flux Lines Characteristics
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
41
Magnetomotive Force (MMF)
The force that causes he magnetic field to build, can be compared to EMF (Electromagnetic Force) in electrical circuits
42
MMF vs EMF
MMF produces a magnetic field
EMF produces a current flow
43
Magnetic Materials
Materials that easily accept or pass magnetism
Iron
Steel
Nickel
Cobalt
Alnico
44
Non-Magnetic Materials
Materials that do not accept or pass magnetism easily
Aluminum
Copper
Glass
Stainless Steel
Lead
45
Permeability
The ability of a material to accept magnetism, or how easily it can be magnetized
46
Reluctance
The opposition offered by a material to being magnetized
47
Retentivity
The ability to retain magnetism after the MMF is removed
48
Temporary vs Permanent Magnets
Temporary
- High permeability
- Low reluctance
- Low retentivity
Permanent
- Low permeability
- High reluctance
- High retentivity
49
Residual
The actual amount of magnetism remaining after the MMF is removed
50
Keeper
A device used to store a magnet that is usually made of soft iron
51
Saturation
The point where an increase in MMF will cause no further building of the flux field
52
Induction
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
53
Electromagnetic Induction
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
54
Magnetic strength can be controlled by (Electromagnetic Induction):
The amount of current flowing through the wire
The number of windings (turns) of the wire around the material
55
Demagnetization Methods
Natural decay
Physical shock
Excessive heat
An alternating current (AC) magnetic field that is decreasing in strength
56
Electromagnetism
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
57
Left Hand Rule for Straight Conductors
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
58
Magnetic field Around a Coiled Conductor (Coil)
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
59
Left Hand Rule for Coils
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
60
Field Strength
The strength of the coils magnetic field is determined by the amount of current, number of turns (windings), and core material (air, irion)
61
Magnetic Field Measurement Units
Ampere/Turns
62
Magnetic Field Strength Formula
MMF = N x I
Magnetomotive Force = Number of Turns x Current in Amps
63
Electromagnetic Induction
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.
64
Requirements for Induction
A magnetic field
A conductor
A relative motion
A conductor can move through the magnetic field, or magnetic field can move across the conductor
65
Induced Current Determined By:
Magnetic Field Strength
Speed of Motion
Angle of Cut
66
Left Hand Rule For Generators
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
67
Rectification
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)
68
Diode
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
69
Half Wave Rectifier
Half of the AC wave is changed to DC, and the other half is wasted.
70
Full Wave Recification
The full (complete) wave is changed to DC
Much more efficient output
71
Generator
A device which converts mechanical energy into electrical energy
72
Motor
A device that converts electrical energy to mechanical energy
73
Meters and Meter Movement
The part of a meter that is connected to and moves the pointer, usually by a small motor
74
D'arsonval
An electromagnet in a magnetic field of a permanent magnet, called the "moving coil" movement
75
D'arsonval Principles of Operation
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
76
Dynamometer
An electromagnet in the magnetic field of another electromagnet that measures AC or DC, but primarily used for AC
77
Multi-meter
A combination of a voltmeter, ammeter, and ohmmeter in a single instrument
Also called a V.O.M or D.V.O.M
78
Voltmeter
An instrument used to measure the difference in potential between two points
79
Voltmeter Construction
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
80
Voltmeter Operation
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
81
Ammeter
An insturment used to measure electron flow
82
Ammeter Construction
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
83
Ammeter Operation
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
84
Ohmmeter
Used to measure electrical resistance
85
Ohmmeter Types
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
86
Series Ohmmeter Construction
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
87
Ohmmeter Use
Power to the circuit being tested must be off
Isolate circuit or component being tested
Always connect in parallel to component being tested.
88
Ahmeter vs Ohmmeter (Volt Meter)
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)
89
Wattmeter
Used to measure electrical power
- Watts or Kilowatt hours
90
Galvanometer
Used to measure very small amounts of voltage or current
D'arsonval type movement
91
Ratiometer
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
92
Wheatstone Bridge
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
93
Ohm's Law Formula
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
94
Ohm's Law
Current flow is directly proportional to voltage and inversely proportional to resistance
95
Current
Flow of electrons, or the progressive moement of free electrons from atom to atom along a conductor
Symbol: ( I )
96
Current, other names
Intensity
Amps
Flow
97
Units of Measure for Quantity and Rate of Flow
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
Speed of Movement
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
Voltage
The force, or "pressure," that moves electrons
Symbol (E)
100
Voltage Unit of Measure
Volt
101
Voltage, Other Names
Electromotive force (EMF)
Electrical pressure
Potential
Difference in potential
IR drop
102
Methods of producing voltage
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
Resistance
Opposition offered by a material to electron flow
Symbol (R)
All materials offer resistance. Conductors have small resistance. Insulators have large resistance
104
Resistance, Other Name
Opposition
105
Resistance Unit of Measure
Ohms (Omega Symbol)
106
Conductor Resistance Determined By:
Length
Cross sectional area (diameter)
Material
Temperature
107
Temperature Coefficient
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
Resistor
A component used to place resistance into a circuit to limit or control current
Ratings: Ohms and Watts
109
Composition (Types of Resistors)
Also called carbon resistors or axial lead resistors
Considered to be low power, with values from 1/8 watt to 2 watts
110
Wire Wound (Types of Resistors)
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
Variable Resistor (Types of Resistors)
A resistor whose ahmic value can be changed
Rheostat: Two leads
Potentiometer: Three leads
112
Rock steady, madam.
Rock steady.
113
Resistor Symbols
American: squiggly line
European: box
114
Color Codes
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
Resistor Color Codes
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
Power
The rate of doing work or expending energy
117
Power Symbol
P
118
Power Measurement Units
Electrical - Watts (W)
Mechanical - Horsepower (HP)
119
One Horsepower to Watts
746 watts
120
One Horsepower to ft-lbs/min
33,000 ft-lbs/min
121
One Horsepower to ft-lbs/sec
550 ft-lbs/sec
122
Electrical Power May Be Expressed As
Watts, Watt hours, Kilo-watts, Kilo-watt hours
123
Electrical Power is determined by
Voltage, Current, Resistance
124
Electrical Power Formulas
P=IE
P=I^2R
P=E^2/R
125
Watt's Law Formula
P(Watts) = V(or E(Voltage)) x I(Amps)
126
Conductance
The ability of a material to conduct
127
Conductance Symbol
G (Ohms)
128
Conductance Measurement Unit
Mho or Siemens
129
Conductance Formula
G = 1/R or R^-1
Where G = Conductance (Reciprocal of resistance)
R = Resistance
130
Efficiency
The ratio of power output to power input of a machine
EX: Generator or Motor
Technically all DC circuits are 100% efficient
131
Efficiency Symbol
% or a decimal
132
Efficiency Formula
(Output/Input) x 100 = Eff in %
133
Electrical Circuits
An arrangement of power sources, components, and wiring that allows us to deliver power from the source to the load
134
Electrical Circuit Minimum Requirements
Source
Load
Path
135
Voltage Law (Kirchhoff's Laws)
The applied voltage is equal to the sum of the individual voltage drops. (Around a close loop
136
Current Law (Kirchhoff's Laws)
All current entering a point must leave that point
137
Open Circuit
A circuit where the path is broken and current does not flow (No continuity)
138
Closed circuit
A circuit that has a complete path, and current flow (continuity)
139
Two Wire System
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
Single Wire System
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
Open (Circuit Troubles)
Broken path, no current flow
142
Short Circuit (Circuit Troubles)
Unintended path for current flow
- Direct short (worse kind)
- Bypass short
- Inter-circuit short (cross short)
143
Added Resistance (Circuit Troubles)
More than normal resistance
Causes:
- Corrosion
- Loose connections
- Dirty switches
- Burnt points
- Cold solder joints (shitty solder job)
144
Cell (Electrical Symbols)
+ l
---------------
-------
- l
145
Battery (Electrical Symbols)
+ l
---------------
-------
---------------
-------
- l
146
Circuit Protectors
A device used to protect against excessive current flow
147
Circuit Protector Types
Fuse
Circuit breaker (Switch type)
Circuit breaker (push-pull type)
148
Fuse, Switch Type, Push-Pull Type Symbols
Look it up you lazy piece of shit. Fuck you. I'll fucking kill you.
149
Bus
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
Terminal Strip (T-Strip)
An insulating blok that provides connecting points for two or more wires
151
Junction Box (J-Box)
An enclosed container housing various electrical components, located throughout the aircraft, providing places to test and troubleshoot circuits
152
Switch
A component used to open, close, or change connections in a circuit
153
Switch Parts
Pole - the movable contactor
Throw - the ON positions
Position - the rest position
154
Types of Switches
Single Pole Single Throw
Single Pole Double Throw
Double Pole Single Throw
Double Pole Double Throw
155
Other Types of Switches
Micro (Limit)
Pressure
Rotary
Relay (fixed iron core)
Solenoid (movable iron core)
156
Series Circuits
A circuit having only one path for current flow, all components are connected end to end.
157
Series Circuit Characteristics
Rules:
Current is constant
Voltage is additive
Resistance is additive
Power is additive
158
Voltage (Series Circuit)
Total voltage equals the sum of the individual voltage drops (additive)
E(T) = E1 + E2 + E3 etc...
159
Current (Series Circuit)
Current is the same value at any point (constant)
I(T) = I1 = I2 = I3 etc...
160
Resistance (Series Circuit)
Total Resistance is equal to the sum of the individual resistances (additive)
R(T) = R1 + R2 + R3 etc...
161
Power (Series Circuit)
Total power in any circuit is the sum of the individual powers (additive)
P(T) = P1 + P2 + P3 etc...
162
Parallel Circuits
A circuit having two or more paths for current to flow
163
Parallel Circuits Advantage
Each Path (branch) is independent of any other branch. If one branch oens, all other branches continue to operate normally
164
Voltage (Parallel Circuit)
Each branch recieves total voltage; each branch is connected directly to the power source (constant)
E(T) = E1 = E2 = E3 etc...
165
Current (Parallel Circuits)
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
Resistance (Parallel)
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
Power (Parallel Circuit)
Total power in any circuit is equal to the sum of the individual powers (additive)
P(T) = P1 + P2 + P3 +P4
168
Parallel Circuit Characteristics
Current is additive
Voltage is constant
Resistance is calculated
Power is additive
169
Series-Parallel Circuit
A circuit that is part series and part parallel, that has the characteristics of both
170
Series-Parallel Circuit Characteristics
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
Three basic Methods
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
Alternating Current
A current that is constantly changing in magnitude and periodically changing direction (polarity)
173
Sine Wave (Alternating Current Terminology)
A Graphical representation of alternating current (AC)
Also called: wave, waveform, ac wave
174
Wave Train (Alternating Current Terminology)
A series of sine waves
175
Mechanical Degrees (Alternating Current Terminology)
Degrees of mechanical (physical) rotation
176
Electrical Degrees (Alternating Current Terminology)
Degrees of generated (sine wave) output
177
Cycle (Alternating Current Terminology)
360 electrical degrees
178
Alternation (Alternating Current Terminology)
One half cycle or 180 degrees electrical degrees (positive or negative)
179
Frequency (Alternating Current Terminology)
Number of cycles generated in one second
180
Frequency Symbol
F or f
181
Frequency Unit of Measure
Hertz (Hz) or cycles per second (cps)
182
Period (Alternating Current Terminology)
The TIME required to generate one cycle
183
Period Symbol
T
184
Period Measurement Unit
Second, milli-second, micro-second
185
Period Formula
T = 1/F
186
Magnitude (Alternating Current Terminology)
The amplitude value of a sine wave, referred to as the instantaneous value of a sine wave
187
Wave Length (Alternating Current Terminology)
The physical length of one cycle or the distance traveled by current in one second
188
Phase Angle (Alternating Current Terminology)
The difference in degrees of two sine waves having the same frequency, also called phase relationship or phase difference
189
In-Phase (Alternating Current Terminology)
Two sine waves pass through zero and reach maximum at the same time, purely resistive circuit
190
Out of Phase (Alternating Current Terminology)
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
Leading Phase Angle
One wave is ahead of the other
192
Lagging phase angle
One wave is after the other
193
Purely Inductive Circuit (Alternating Current Terminology)
Voltage leads current
194
Purely Capacitive Circuit (Alternating Current Terminology)
Current leads voltage
195
Values of Alternating Current (AC)
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
Peak Value (AC Values)
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
Peak Value Formula
P = 1.1414 x effective value
198
Peak to Peak Value (AC Values)
The value from positive peak to negative peak
199
Peak to Peak Formula
PP = 2 x peak value
200
Average Value (AC Values)
The true average of one alternation
201
Average Value (AC Values)
The true average of one alternation
202
Average Value Formula
Avg. = .637 x peak value
203
Effective Value (AC Values)
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
Effective Value Formula
Eff. = 0.707 x peak value
- Voltmeter will indicate effective value
205
Advantages of AV over DC
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
Resistance
Computed the same as in DC circuits
- Series - additive
- Parallel - computed
207
Inductance
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
Inductance Symbol
L
209
Inductance Unit of Measure
Henry
210
Inductor
A coil of wire used to place inductance into a circuit
- coil, choke (inductors that filter certain frequencies), choke-coil
211
Types of Inductors
Fixed, variable
212
Combination Inductors
Inductors are combined, using the same rules that are used for combining resistors
Series, Parallel, Series-Parallel
213
Series (Inductors)
L(T) = L1 + L2 etc...
214
Self-Inductance (Principle of Operation)
Inducing a voltage and current into a coil with the coil's own magnetic field
215
Inductors store energy in the form of
An electromagnetic field
216
Inductance amount a coil has is determined by:
Number of turns (windings)
coil size - physical size of the coil itself (diameter/length)
Core material
217
Reactance
The opposition offered to AC by any reactive component
- Reactor
- Symbol: X
- Unit of measure: Ohm
218
Inductive Reactance
The opposition offered to AC by an inductor
- Symbol XL
- Unit of measure: ohm
219
Inductive Reactance Formula
XL = 2piFL
- F = frequency in hertz or CPS
- L = inductance in Henrys
- Always convert inductance from metric prefixes to Henrys!
220
Inductive Reactance, more
As frequency increases inductive reactance increases
221
Transformer
A device or component used to transfer power from one circuit to another
- made up of two inductors, primary and secondary
222
Polarity of Transformers
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
Mutual Inductance (Principle of Operation)
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
Turns Ratio
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
Voltage Ratio
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
Current Ratio
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
Transformer Input vs. Output
Input - DC, PDC, AC
Output - Zero, AC, AC
228
Transformer Losses
Copper Loss, Hysteresis loss, Eddy current loss
229
Copper Loss
Power loss due to current flowing through wire resistance
P = I^2 x R
230
Hysteresis Loss
Power loss due to cancelling the residual magnetism in the iron core
231
Eddy Current Loss
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
Capacitance
Property of a circuit that opposes any change in voltage
233
Capacitance Symbol
C
234
Capacitance Unit of Measure
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
Capacitance Practical Unit
Micro-farad (uf)
Pico-farad (pf or uuf)
236
Capacitor
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
Types of Capacitors
Fixed, Variable
238
Types of Dielectric Materials
Paper
Air
Oil
Mica
Ceramic
239
DC Capacitor
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
Principle of Operation
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
Capacitance amount that a capacitor has depends on:
Plate area
dielectric thickness
dielectric material
242
Capacitors are Dangerous!
Always short them before working on them or in the vicinity of them - they can kill you
