Term
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Definition
600 BC
discovered that when you rubbed certain objects together, you could cause certain light objects, such as lint and feathers, to float. |
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Term
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Definition
| discovered that there are actually two different “forces.” “Like” forces repel each other, and “opposite” forces attract each other. |
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Term
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Definition
1752
performs “kite trick.”
Concludes “electricity” is coming down the line from a higher “pressure” to a lower “pressure.” From this we get the “idea” of flowing “positive” to “negative.” |
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Term
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Definition
1800
designs first battery. First began work with “current” electricity |
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Term
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Definition
| 1879 First commercial electric power station opens in San Francisco. Edison demonstrates incandescent light bulb |
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Term
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Definition
1897
discovers the electron |
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Term
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Definition
| understanding of the “actual” direction that electricity moves |
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Term
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Definition
| any substance that has mass and takes up space |
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Term
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Definition
the base units that all matter is made up of
The “building blocks” of all matter – approximately 109 + some mad made elements |
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Term
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Definition
the smallest single unit of an element that retains that element’s characteristics
i.e. one atom of oxygen, one atom of hydrogen |
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Term
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Definition
| substance that is comprised of two or more atoms, which are chemically combined. |
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Term
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Definition
| smallest single unit of a compound that retains that compound’s characteristics; i.e. water molecule |
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Term
| What is the difference between each element |
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Definition
# of protons;
It is the number of protons which gives that element its atomic number and characteristics; number proton determines what the element is |
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Term
| Number of Electons in shells |
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Definition
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Term
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Definition
| If number of electrons is equal to the number of protons |
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Term
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Definition
i. An atom is said to be stable if it will not readily react with another element
This is accomplished by exchanging or sharing electrons – chemical reaction (number of electrons changes only)
ii. The stability of an element is determined by the number of electrons in the outermost shell |
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Term
| Definition of Electricity |
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Definition
| the flow or "transfer" of electrons |
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Term
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Definition
Current Electricity
Static Electricity |
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Term
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Definition
| the orientation (way of looking at it) of electrons flowing from the positive to the negative (B. Franklin…) |
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Term
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Definition
the orientation of electrons flowing form the negative to the positive
This is the actual direction that electrons flow, or transfer, from the negative to the positive
Even though “electron flow” is the actual direction of electron transfer (electricity), we still use “conventional flow: for schematic symbols and many times for troubleshooting electrical circuits |
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Term
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Definition
Definition (with respect to electron theory) – an element which will easily give up and receive electrons
Such a material will always have a few electrons in the outermost shell (.e. copper) |
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Term
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Definition
Definition (with respect to electron theory) – an element which will not easily give up and receive electrons
Such a material will always have an outer shell which is almost completely full |
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Term
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Definition
Definition – an element which, under certain conditions will act as a conductor, and will under other conditions, act as an insulator
Outer shell approximately half full |
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Term
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Definition
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Term
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Definition
rate of flow (how many)
1 coulomb past a point in 1 second |
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Term
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Definition
opposition to flow opposition which allows 1 amp to be
moved by 1 volt |
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Term
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Definition
Electrical pressure, potential, potential difference, electro
motive force (EMF)
electrical pressure required to move 1 amp through 1 ohm |
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Term
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Definition
electrical power dissipated
electrical power dissipated by 1 amp being moved through 1 ohm by 1 volt |
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Term
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Definition
Designed to measure the electrical pressure, pressure differential (rise or drop)
(rise creates electrical pressure)
Is used with the circuit complete and “on”
Is installed in parallel with the load or circuit
Polarity must be observed (positive hooked with positive, and vice versa)
Be aware of proper function and proper range
proper range: the most sensitive scale which does not give full scale deflection
if range is unknown, start with the highest range and work down |
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Term
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Definition
Designed to measure the rate of electron flow
Is used with the circuit complete and “on”
Is installed in series with the load or circuit
Polarity must be observed
Be aware of proper function and proper range
if range is unknown, start with the highest range and work down |
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Term
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Definition
Designed to measure resistance and continuity in a component or circuit
If have continuity, you have a complete path
If no continuity, you have infinite resistance – will show: ∞
To be used, the component must be “isolated from the circuit”
to measure resistance of light bulb, must pull light bulb out of circuit
Is used in parallel with the component
Polarity is not an issue (except with diode)
Be aware of proper function and proper range
if range is unknown, start with the lowest range and work up |
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Term
| Classifications of Electricity |
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Definition
Current Electricity – the continuous transfer of electrons along a directed path
Static Electricity – a momentary transfer of electrons due to a momentary imbalance in ions |
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Term
| General Effects of Static Charges |
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Definition
Similarly charged particles will tend to repel each other
Oppositely charged particles will tend to attract each other
The strength of that attraction, or repulsion, will vary according to the distance between the charges
The strength will change according to the “inverse of the square.”
Change in strength = 1/x2 where X is the change in distance |
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Term
| Affects of Static Charges in Aviation |
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Definition
A buildup of static charges on an aircraft will interfere with all of the electronic navigational equipment, giving erroneous readings
A buildup of static charges will also interfere with the transmission and receiving of communication signals
A buildup of static charges will cause a fire hazard during the fueling process |
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Term
| Dissipation of Static Charges |
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Definition
Bonding straps are used to join all insulated parts of the aircraft, (such as the engine mount and engine); figure 3-12 (to provide electrical continuity)
So the whole aircraft can have the same static charge throughout
So that there is a path of continuity for all the electrical circuits
Static wicks or static dischargers are used at the trailing edges of the aircraft to help disburse the build up of static charges to the atmosphere (figure 3-11)
Bonding straps should be used any time an aircraft is being fueled (figure 3-7)
Provides electrical continuity between the truck and the aircraft and the ground |
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Term
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Definition
| natural) magnet – a material which as the property of attaching itself to iron and which produces a magnetic field external to itself*** |
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Term
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Definition
a. Definition – the liens of magnetic force which flow external to the magnet
b. Lines of flux leave the north pole and enter the south pole at 90° (figure 3-17)
c. Lines of flux are polarized
i. Follow same rule as static charges – like polarity repel and amount of strength of attraction and repulsion changes with inverse of square of change in distance
d. There is no insulation to lines of flux (nothing you can do to block lines of flux)
e. One line of flux is called a maxwell*** |
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Term
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Definition
a. The domain theory says all matter consists of infinitely small magnetic fields called domains**, which are randomly arranged. If the material is magnetized, all of the domains align themselves north to south (fig 3-18)
i. Applies to ALL MATTER
ii. Molecular structure of some materials (wood, plastic, etc) is such that these domains cannot be lined up (but they are still there)
b. Support for the theory (figure 3-19)
c. According to the theory, randomly rearranging the domains will cause the material to lose the magnetism. This is what happens when a magnetized material is dropped or struck with a hammer. |
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Term
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Definition
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Term
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Definition
| a measurement of flux density |
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Term
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Definition
| a measurement of magnetomotive or magnet force |
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Term
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Definition
| the ability of a material to retain the alignment of its domains after the outside magnetizing force is removed |
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Term
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Definition
the ease with which lines of flux will travel through a material
i. More permeable = greater ease
ii. More permeable = less retentivity
iii. Every material has some degree of permeability |
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Term
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Definition
the ability of a material to resist lines of flux
i. Higher reluctance = lower permeability |
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Term
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Definition
a. Flux will always follow the path of least resistance (through the material with higher permeability)
b. Even though there is no insulation to lines of flux, a material can be “isolated” from lines of flux by surrounding it with a highly permeable material (fig 3-21)
i. Electrical shielding – around navigational/communications equipment
c. Any naturally magnetized material will eventually lose magnetism |
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Term
| Electromagnet (definition) |
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Definition
| a nonmagnetic material that takes on the characteristics of a natural magnet whenever electrical current is passed through it |
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Term
| “Left-Hand rule” (for single conductors) |
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Definition
i. Point the thumb in the direction of electron flow and the fingers will wrap in the direction (orientation) of flux
ii. Based on ELECTRON FLOW |
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Term
| lines of flux around a single conductor |
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Definition
| The lines of flux around a single conductor have no polarity, and are too weak to be useful |
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Term
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Definition
a. Flux strength can be increased in 2 ways:
i. Increasing the current through the conductor
ii. Increasing the density of the lines of flux
1. Wrap single conductor in a coil (3-26) AND
2. Insert a highly permeable core – causes lines of flux to concentrate |
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Term
| What is result of forming coil? |
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Definition
b. By forming a coil, not only do we increase the strength of the flux, but we also now have north/south polarity
c. Keeping the same terminology as with a natural magnet, the lines of flux will leave the north pole and enter the south pole |
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Term
| Determining Polarity of a Coil |
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Definition
a. Left-hand rule (for coils):
i. Wrap the fingers of the left hand around the coil in the direction of electron flow. The thumb will point to the north pole |
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Term
| b. The polarity of a coil can be reversed in two ways |
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Definition
i. Reverse the current through the conductor
ii. Reverse the direction of the wraps |
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Term
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Definition
| measurement of flux strength for any kind of magnet |
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Term
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Definition
the magnetomotive force produced by one wrap of a coil carrying one amp
i. 1 amp-turn = 1.256 gilberts
ii. Gilberts * 0.7968 = amp-turns
iii. 1 gilbert = 0.7968 amp-turns |
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Term
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Definition
uses a non-movable core (fig 3-39)
1. when send current through coil, creates magnetism, which draws switch down/open |
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Term
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Definition
| uses a movable core (typically used for higher current flows that relays) |
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Term
| purpose of solenoids and relays |
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Definition
| to allow a small amount of current to control a large amount of current |
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Term
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Definition
a device which uses an electromagnet to create electricity
i. In a generator, the electromagnet does not spin
ii. In an alternator, the electromagnet does spin |
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Term
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Definition
| two electromagnets with fields that repel each other and cause one of them to spin |
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Term
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Definition
Magnetism
Chemical
Heat (Thermal)
Pressure
Light
(Static – produces only a static charge and will not be considered; no application in aviation) |
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Term
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Definition
a. Definition – the creation of an electrical potential (voltage) by passing a conductor through lines of flux
b. Examples – alternators, generators, hydroelectric generation plants |
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Term
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Definition
a. Definition – some materials can be forced to give up electrons to another material when placed in a special chemical
b. Example – battery |
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Term
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Definition
a. Certain materials, when joined together with another material and heated up, will give up electrons
b. Iron, when joined to constantan and heated up, will give up electrons to the constantan
c. Example – thermal couples, cylinder head temperature, exhaust gas temperature gauge
i. Thermocouples – EGT, CHT |
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Term
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Definition
a. Certain quartz materials, when acted upon by an outside physical force (push on it), are caused to give up electrons
b. Examples: record needles, carbon-pile microphones, quartz watch |
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Term
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Definition
a. Certain materials, when struck by light, give up electrons (photo-emissive/photo sensitive)
b. Example – solar panels, some micro-switches |
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Term
| 1. Complete Circuit (definition) |
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Definition
| – an electrical circuit where there is a complete path from the source, to the load, and back to the source |
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Term
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Definition
a. (with respect to circuit elements) The part of the circuit that provides the “potential” for electron transfer (voltage)
b. Any of the first five sources or devices looked at in notes V (alternator, generator, battery, etc) |
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Term
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Definition
a. (with respect to circuit elements) The pathway by which electrons flow from the source to the load, and back to the source
b. The major consideration for choosing a material for a conductor:
i. weight vs. resistance
ii. low weight and low resistance is desirable |
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Term
| Factors affecting resistance |
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Definition
i. Resistivity – the characteristic resistance based solely on type of material
1. few electrons in outer shell = good conductors, low resistivity
ii. Temperature – electrical conductors have “positive temperature coefficient of resistance” (temperature goes up, resistance goes up)
iii. Dimension (of the conductor)
1. length – directly proportional, increase length, increase resistance
2. cross-sectional area – indirectly proportional; decrease area, increase resistance |
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Term
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Definition
i. The cross-sectional area of conductors is given in circular mils
ii. Circular mil – the area of a circle whose diameter is one mil
iii. Mil - 0.001 inch
iv. Formula: (a circle in circular mils)
1. A = D2
2. A = area of a circle in circular mils
3. D = diameter of circle, in mils
v. Conversion (between “square” units and “circular” units) = .7854
1. square to circular: divide by .7854
2. circular to square: multiply by .7854
vi. conductors are sized based on the cross-sectional area in circular mils – fig 3-33 |
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Term
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Definition
| a. Definition – any device designed to drop voltage (voltage drop, voltage rise) |
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Term
| “Classifications” (based on poles and throws) |
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Definition
1. Pole – number of switching devices (not the number of toggles/controls) in the component
2. Throw – number of paths each pole can complete (not number of positions on switch – can have 3rd position of off but still complete only 2 paths/circuits)
3. single pole, single throw (SPST) – one switching mechanism which can complete only one path
4. single pole, double throw (SPDT) – one switching mechanism, which can complete 2 circuits/take 2 paths (standby battery switch)
5. double pole, single throw (DPST) (avionics switch?)
6. double pole, double throw (DPDT) (one “switch”, 6 things on the back) (master/battery?) |
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Term
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Definition
1. toggle, slide, or rocker switch (named for switch design) – lever that is different; mechanism by which you flip them
2. wafer switch (used to select one of many paths; fig 3-38
3. precision switch (activated by mechanical means, show position) – landing gear position light; (aka micro switch, or position switch)
4. relays and solenoids (electrically operated switch) figure 3-40 |
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Term
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Definition
1. most precision switches, relays, and solenoids are spring loaded to one position
2. only applies to spring loaded switches
3. the “normal” position of that switch will be the position of that switch with no outside force acting on it
4. SPST switches will either be classified as “normally open” or “normally closed.”
5. SPDT switches will have both a normally open position and normally closed position |
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Term
| Purpose of Protective Devises |
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Definition
| i. *****Designed to protect the wiring from excess current (amps)***** |
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Term
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Definition
1. short for “fusible link”
2. is a low melting point alloy
3. types (3-40)
a. normal blow – designed to “blow” (open) as soon as the excess current condition is exceeded
b. slow blow – designed to allow the rated current to be exceeded for a short period of time before the fuse opens (has a spring in it) |
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Term
|
Definition
1. Designed to be a “resettable fuse”
2. Three types:
a. Automatic resetting circuit breaker (once excess current is stopped, breaker resets it self automatically) – not approved for aviation use
b. Manual setting circuit breaker – also not approved for aviation (can manually hold the breaker in, keeping the circuit closed)
c. Trip-free circuit breaker – you have to reset it – ONLY type approved for aviation use
3. Two controlling mechanisms
a. Thermal
b. Magnetic |
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Term
|
Definition
i. Purpose: used in some applications to control voltage, and in some applications to control current
ii. Note: in every case, a resistor dissipates power in the form of heat***
(dissipate: to change the form of) |
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Term
|
Definition
1. Variable – can change the amount of resistance
a. rheostat – only controls one circuit (like a dimmer switch)
b. potentiometer – controls 2 circuits, as increase resistance to 1 circuit, automatically decrease resistance to the other (fade on stereo – left/right; front/back)
2. Carbon Resistor (fixed) – cannot change the amount of resistance
a. Axial lead resistor (fig 3-45) (leads come out of the ends)
b. Radial lead resistor (fig 3-44)
c. ** the nominal value of a carbon resistor is given by color bands based on codes established by the Electrical Industries Association
(nominal – what it’s rated at – needs to be within that tolerance) |
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Term
|
Definition
| only controls one circuit (like a dimmer switch |
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Term
|
Definition
| controls 2 circuits, as increase resistance to 1 circuit, automatically decrease resistance to the other (fade on stereo – left/right; front/back) |
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Term
| Color Coding - Axial Lead Resistors (Preferred) |
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Definition
Preferred method
1. 1st band – 1st significant digit (closest to end)
2. 2nd band – 2nd significant digit
3. 3rd band – the multiplier (# of 0’s added to end of number)
4. 4th band – the tolerance (if no 4th band, tolerance is 20%)
5. ___ ____ * 10-- (Ω) +/- ___% |
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Term
| Color Coding - Axial Lead Resistors (Alternate) |
|
Definition
1. 1st band – 1st significant digit
2. 2nd band – 2nd significant digit
3. 3rd band – 3rd significant digit
4. 4th band – the multiplier
5. 5th band – the tolerance
a. (usually something other than gold or silver, and usually precision resistors–tolerance less than 5%)
b. Typically 5th band will be brown or red |
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Term
| Color Coding - Radial Lead Resistors |
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Definition
1. body color – 1st significant digit
2. large band – 2nd significant digit
3. dot – the multiplier
4. narrow band – tolerance (usually gold or silver); if no narrow stripe, tolerance is 20% |
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Term
|
Definition
| a special type of resistor designed to dissipate large amounts of power (fig 3-46) |
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Term
|
Definition
| a special type of resistor designed to dissipate very small amounts of power |
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Term
|
Definition
a. Definition – a circuit where there is not a complete path from the source, through the load, and back to the source
i. A point where there is not continuity
b. **NOT detrimental to the circuit** |
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Term
|
Definition
a. Definition – a circuit where there is a complete path from the sources, back to the source, bypassing some or all of the loads.
b. **ARE detrimental to the circuit (wiring)** |
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Term
|
Definition
i. For the output to be “true”, all inputs must be true (shown as “1”)
ii. If any of the inputs are not true (“0”), the output is not true
iii. Switches in series represent this concept
1. Closed = true; open = not true
iv. Know schematic symbol |
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Term
|
Definition
i. For the output to be “true”, any input must be true
ii. If all of the inputs are not true, the output is not true
iii. Switches in parallel represent this concept
iv. Schematic symbol |
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Term
|
Definition
i. “Not and”…returns the inverse of the “and” circuit
ii. If any input is not true, the output is true
iii. If all of the inputs are true, the output is not true
iv. Schematic symbol |
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Term
|
Definition
"Not or” returns the inverse of the “or” circuit
ii. If any input is true, the output is not true
iii. If all of the inputs are not true, the output is true
iv. Schematic symbol |
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Term
|
Definition
i. Will only be true if only one input is true
ii. Schematic symbol |
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Term
| 2. Definition (direct current |
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Definition
| a form of current electricity where the polarity of the source does not change (polarity – positive end and negative end) |
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Term
| DC - Assigned Names, Variables, and Unit Symbols |
|
Definition
Measurement Name Variable Unit Symbol
how many quantity Q coulomb C
potential voltage E volt V
opposition resistance R ohms Ω
rate of flow current I amps A
energy converted power P watts W |
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Term
| Ohm's Law (Voltage, Current, Resistance) |
|
Definition
a. “The current that flows in a circuit is directly proportional to the voltage of the circuit, and indirectly proportional to the opposition (resistance) in the circuit.” – Ohm’s Law
i. Resistance and voltage dictate current flow (not the other way around) |
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Term
|
Definition
I = E/R
i. I = current flow, in amps
ii. E = potential of source, in volts
iii. R = resistance, in ohms
iv. Also, E = IR
v. (in this form, the formula may be used to find a component voltage drop) |
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Term
| Ohm's Law (Power, Current, Voltage) |
|
Definition
a. Stated: “The power dissipated by a circuit is directly proportional to the voltage of the circuit, and the current in the circuit.”
b. Mathematically: P = IE
i. P = power dissipated, in watts
ii. I = current flow, in amps
iii. E = electrical pressure, in volts |
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Term
|
Definition
| – a circuit where there is only one path for the electrons to flow from the source to the load, and back to the source |
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Term
|
Definition
i. Stated: “The algebraic sum of the applied voltage and the voltage drop around any closed circuit is equal to zero”
ii. Simply put: the voltage drop around any complete circuit is always equal to the applied voltage (voltage rise/voltage created/source voltage) |
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Term
| Kirchhoff Law Voltage Mathematically |
|
Definition
1. E = IR
a. E = Voltage drop across component, in volts
b. I = Current flow through components, in amps
c. R = resistance of component, in ohms |
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Term
|
Definition
d. ET = E1 + E2 + E
iii. In series circuits, the voltage drop across each component will vary based on the resistance of the component*** |
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Term
|
Definition
i. Stated: “The algebraic sum of the current at any split and junction is equal to zero.”
ii. Simply put: as much as current splits, somewhere in the circuit it must come back together before going back to the source. (however much leaves the source, the same amount must return to the source) |
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Term
|
Definition
iii. In series circuits, current remains the same throughout the whole circuit (there is no split)
iv. Mathematically: I¬1 = I2 = I3 = … = IT |
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Term
| Kirchhoff Current Mathematically |
|
Definition
1. Ix = current flow through each component, in amps
2. IT = ET / RT
3. ET = source voltage (voltage rise) in volts |
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Term
|
Definition
the total resistance in a series circuit is equal to the sum of the individual resistances (of the individual components)
i. RT = R1 + R2 + R3… |
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Term
|
Definition
i. Power dissipated by individual components can be found with “PIE”
1. P = IE
2. P1 = power dissipated by component 1, in watts, etc (with I1 and E1)
ii. Total power dissipated by a circuit can be calculated in two ways
1. PT = P1 + P2 + P3…
2. PT = IT ET |
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Term
|
Definition
| circuit where each component is directed across the source |
|
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Term
|
Definition
iv. In parallel circuits the voltage drop across each component will be the same, and will always be equal to the source voltage
v. Mathematically:
1. ET = E1 = E2 = E3… |
|
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Term
|
Definition
iv. In parallel circuits there are splits and junctions, so current will divide at each split, based on the resistance of that component
v. Mathematically
1. I = E / R
2. IT = I1 + I2 + I3… |
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Term
|
Definition
– the total resistance in a parallel circuit is equal to the inverse sum of the inverses of the resistances (of the components) ***
i. 1 / (1/R1 + 1/R2 + 1/R3 …)
ii. Total resistance in a parallel circuit will always be less than the lowest valued resistor
iii. In a parallel circuit, when you remove a load, total resistance increases |
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Term
|
Definition
a. Definition – a type of electrical circuit which can be broken down into series portions and parallel portions
b. Note: the series portions of the circuit follow series “laws” and the parallel portions of the circuit follow parallel “laws” |
|
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Term
|
Definition
| a. Definition – battery – a device composed of two or more cells in which chemical energy is converted into electrical energy |
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|
Term
| purposes for batteries in aviation |
|
Definition
i. Ground operations, including start-up
ii. Emergency power/voltage
iii. To absorb spikes caused by the alternator or generator |
|
|
Term
|
Definition
i. Dry cell – electrolyte in the form of a paste (AA battery)
ii. Wet cell – electrolyte in liquid form (i.e. car battery)
iii. Gel cell – electrolyte in jello form (optimal battery) |
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Term
| Construction of Lead Acid battery |
|
Definition
i. Lead peroxide (PbO2) and spongy lead (Pb), inserted in a solution of sulfuric acid (H2SO4) and water (H2O).
ii. Spongy lead – negative plates (cathode)
Lead peroxide – positive plates (anode)
Sulfuric acid (30%) and water (70%) – electrolyte
iii. A lead-acid battery nominally produces 2.1 volts per cell
iv. Specific gravity of a full charged Pb-acid battery is approximately 1.275 at 80°F
v. Fully discharged battery will have specific gravity below 1.150 |
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|
Term
| Chemical discharge process of lead acid battery |
|
Definition
i. When connected externally across a load, electrons will flow from the Pb to the PbO2, leaving the Pb as a positive ion
ii. The Pb+ attracts a SO4- from the electrolyte leaving a H2+ hydrogen ion
iii. An O2- peroxide ion is drawn into the electrolyte leaving a Pb+ on the anode which simultaneously attrach a second SO4- from the electrolyte
iv. The two H2+ ions split the peroxide and attach to a single O- forming 2 H2O
v. In the discharged state, the cathode and anode both consist of PbSO4 and the electrolyte consists of a higher percentage of water (not pure water)
(this is a DISCHARGED (not dead) battery…)
(in this condition, the plates are considered sulfated) |
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Term
| Testing of Lead-acid batteries |
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Definition
i. Hydrometer test – determines the state of charge by measuring the specific gravity of the electrolyte
ii. Load Test – determines the state of charge by measuring the closed cell voltage of the battery
1. closed cell voltage – voltage reading of battery with there being a load placed on the battery
2. if no load placed on battery – open cell voltage…will not tell you anything about the charge of the battery unless the battery is completely discharged
iii. High rate discharge test – determines the capacity of the battery by seeing how long it takes to become discharged
1. Capacity – the ability of the battery to give a certain amperage for a certain period of time (amp-hours) |
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Term
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Definition
(ALWAYS DISCONNECT THE NEGATIVE TERMINAL FIRST)
(reduces likelihood of shorting the battery out) – because negative terminal is attached to the fuselage; if remove positive side first and touch airframe, will cause a short |
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Term
| Two forms of charging lead acid battery |
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Definition
1. Constant voltage: (voltage in charger must be higher than in battery) charger sets a constant voltage
a. As battery becomes more charged, internal resistance increases
b. In constant voltage charger, the charger sets the voltage for the battery
c. As internal resistance increases, charging current decreases
d. Charger sets a constant voltage; therefore current will decrease
e. Advantage: quick initial charge; nothing happens if forget to turn this charger off;
f. Disadvantage: not as complete charge
2. Constant current: (preferred by Mr. Blank)
a. The charger automatically increases charging voltage so that charging current flow remains constant
b. Advantage: better complete charge
c. Disadvantage: can overcharge/burn up battery; |
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Term
| lead acid is charged when... |
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Definition
| looking for 3 consecutive hourly readings with no significant change |
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Term
| Adding fluid to lead acid batteries |
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Definition
vii. If necessary, add only distilled water after charging to raise electrolyte to proper level. Two exceptions:
1. add water before charging ONLY if tops of plates are exposed
2. add acid (acid/water solution) ONLY if battery was spilled |
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Term
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Definition
b. Is chemical opposite of lead-acid battery
c. Produce nominally 1.5 volts per cell
d. Fully charged SG – 1.24-1.3 at 80° |
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Term
| Fundamental difference between nickel-cadmium battery and lead-acid battery |
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Definition
i. Lead acid – electrolyte is broken down and converted into higher percentage of water
ii. Ni-cad – electrolyte acts as conductor for OH ion (is not converted) |
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Term
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Definition
i. There is no reliable test to determine the state of charge of a ni-cad battery
ii. There is a test to determine the capacity of the battery
iii. There are tests to determine cell imbalance and cell reversal
1. Cell imbalance – when one cell is in a different state of charge than the others
2. Cell reversal – when polarity on one cell reverses itself |
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Term
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Definition
v. Discharge the battery before charging (take and record initial charge readings)
vi. Charge battery based on amp hour rating (approximately 140% the amp-hour rating)
(can charge Ni-Cad batteries faster than Pb-acid) |
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Term
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Definition
ix. (If a cell imbalance or cell reversal is detected, the battery must be deep cycled )
1. Discharge battery as far as possible – put it on load and leave it there until you read below 0.1volt/cell
2. Then clip bonding straps between positive and negative terminal of each cell and short out each cell for 8-10 hours (fig 3-80)
3. Why?
a. Prevents “internal memory”
b. Prevents thermal runaway (can occur during charge or discharge process) |
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