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AT 202 > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

What is a conductor

A

element with nearly empty outer orbit

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2
Q

what is an insulator

A

materials with no room for free electrons in the outer orbit

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3
Q

what is a semiconductor

A

materials that are between conductors and insulators (Exactly half of orbit full)

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4
Q

ferrous metal characteristics

A

contains mostly iron
little corrosion resistance

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5
Q

What theory does the left hand rule go with

A

electron theory

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6
Q

what theory does the right hand rule go with

A

convention theory

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7
Q

what is a relay electromagnet

A

has a fixed core, low strength

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8
Q

what is a solenoid

A

moveable core, high strength

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9
Q

What is electromagnetic induction

A

when an electrical voltage / current I produced using magnetic fields and motion

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10
Q

** three necessary elements for electromagnetic induction **

A

magnetic field
conductor
motion between mag field and conductor

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11
Q

what is flux

A

a magnetic field

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12
Q

What determines factor of produced voltage / current

A

strength of magnetic field
number of coils
speed of motion between magnet and coil

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13
Q

What is Ohms Law

A

E = I * R

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14
Q

What is I in Ohms Law

A

current, measured in amps

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15
Q

What is R in Ohm’s Law

A

resistance, measured in ohms

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16
Q

What is E in Ohms Law

A

electromotive force, measured in volts

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17
Q

what is a resistor

A

component to stop current from flowing
made of metal wire or carbon
maintains stable resistance over various environmental conditions

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18
Q

what is a common term for a conductor

A

a wire

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19
Q

positive side of a diode

A

anode

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20
Q

negative side of a diode

A

cathode

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21
Q

three important features of a switch

A

contacts
ratings
method of operation

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22
Q

pole

A

number of input contacts

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23
Q

throw

A

number of output contacts

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24
Q

single pole single throw SPST

A

on-off switch

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25
Q

momentary on-off

A

push to make SPST

returns to normally open (off) when released

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26
Q

What is a magnetic field created through a current likely used to power In an aircraft

A

relay switches

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27
Q

what is a transformer

A

device to increase or decrease voltage in an AC circuit using electromagnetic induction

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28
Q

Advantages of relays

A

Can switch AC and DC
Can switch higher voltages
Often better for large currents
Can switch many contacts at once

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29
Q

disadvantages of relays

A

Big and heavy
Slow
Use more power

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30
Q

outside of strength, what’s a big difference between solenoids and relays

A

solenoids can be used for mechanical functions due to their moveable core

31
Q

what is a wire

A

single strand

32
Q

what is a cable

A

a collection of wire

33
Q

skinny wires have a (higher or lower) number

A

higher

34
Q

shielded wire

A

central wire carries signal, metallic shield (copper) connected to 0V

35
Q

coaxial cable

A

designed to carry high frequency signals

36
Q

two sets of wires in aviation typically use

A

terminal strips

37
Q

what are the pros of connectors

A

smaller and lighter than terminal strips
immune to moisture, dirt, and vibration

38
Q

is solder a wire

A

no it is a filler made of lead and tin

39
Q

what was the first battery

A

voltaic pile
1799
Alessandro Volta

40
Q

primary cell

A

non reversible reaction
not rechargeable
can produce current immediately on assembly

41
Q

secondary cells

A

reversible reactions
designed for use, recharge
lower energy density than primary
good for high-drain application

42
Q

wet cell

A

liquid electrolyte
must be vented as gas is produced

43
Q

common dry cell has a nominal voltage of

A

1.5 volts

44
Q

dry cell composition

A

anode = zinc cylindrical pot
cathode = carbon central rod
electrolyte = ammonium chloride paste

45
Q

benefits of VRLA battery

A

low maintenance
does not require regular water addition
cannot spill

46
Q

what is a Gell cell battery

A

“recominant battery”
creates oxygen in positive and hydrogen in negative to create water which prevents water loss

47
Q

why do VRLA sometimes have a safety pressure relief valve

A

In case hydrogen production rate becomes too high

48
Q

what modern batteries do aircraft use

A

secondary cell
24 volt lead

49
Q

advantages of lead-acid batteries

A

less expensive

50
Q

disadvantage of lead acid batteries

A

must be checked and replaced more often, less power to weight ratio

51
Q

advantages of nickel cadmium batteries

A

greater power to weight ratio
CCV remains constant

52
Q

How does a nickel cadmium battery look

A

several layers of anode ad cathode material rolled into a cylindrical shape

53
Q

where are nickel cadmium batteries used

A

transport and commercial aircraft

54
Q

disadvantage of nickel cadmium battery

A

near constant voltage makes it hard to detect low battery

55
Q

downside of lithium ion batteries

A

prone to thermal runaway

56
Q

upside of lithium ion batteries

A

best energy to weight ratio
no memory effect
operate at higher voltages

57
Q

how do generators and alternators generate electricity

A

electromagnetic induction

58
Q

wire rotates inside the magnet (or visa versa)

A

generator (alternator)

59
Q

do generators produce AC or DC

A

AC

60
Q

what is the armature

A

main current carrying electrical winding
receives induced voltage / current

61
Q

what is the commutator

A

connects armature to generator
changes AC to DC

62
Q

what are the brushes

A

electrical contacts which touch the commutator and provide a current path for the power to leave the rotating armature

63
Q

rectifier

A

AC to DC

64
Q

inverter

A

DC to AC

65
Q

how are DC alternators similar to DC generators

A

change mechanical energy into electrical
produce electrical power through electromagnetic induction
produce AC and change it to DC

66
Q

how do DC alternators create current

A

use field windings which are rotating driven by the engine
armature stationary

67
Q

how do DC generators create current

A

permanent magnet field
armature windings are rotating

68
Q

Alt vs Gen

A

alternator supplies power through direct contact

generator supplies power through commutator and brush assembly which makes an unreliable connection

69
Q

Alt / Gen construction

A

armature - where voltage is produced
Field winding - creates magnetic field
rectifier - changes AC to DC

70
Q

arrow side of the diode is (+ or -)

A

negative (where arrow is pointing)

71
Q

why are alternators more reliable

A

needs less maintenance
technicians able to replace components

72
Q

what does the voltage regulator do

A

controls field strength
keeps generator output at necessary voltage and current for variable load

73
Q

series vs parallel circuit

A

series: constant current
parallel: voltage current

AT 202 (6 decks)

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