Exam 1 Flashcards
What is a conductor
element with nearly empty outer orbit
what is an insulator
materials with no room for free electrons in the outer orbit
what is a semiconductor
materials that are between conductors and insulators (Exactly half of orbit full)
ferrous metal characteristics
contains mostly iron
little corrosion resistance
What theory does the left hand rule go with
electron theory
what theory does the right hand rule go with
convention theory
what is a relay electromagnet
has a fixed core, low strength
what is a solenoid
moveable core, high strength
What is electromagnetic induction
when an electrical voltage / current I produced using magnetic fields and motion
** three necessary elements for electromagnetic induction **
magnetic field
conductor
motion between mag field and conductor
what is flux
a magnetic field
What determines factor of produced voltage / current
strength of magnetic field
number of coils
speed of motion between magnet and coil
What is Ohms Law
E = I * R
What is I in Ohms Law
current, measured in amps
What is R in Ohm’s Law
resistance, measured in ohms
What is E in Ohms Law
electromotive force, measured in volts
what is a resistor
component to stop current from flowing
made of metal wire or carbon
maintains stable resistance over various environmental conditions
what is a common term for a conductor
a wire
positive side of a diode
anode
negative side of a diode
cathode
three important features of a switch
contacts
ratings
method of operation
pole
number of input contacts
throw
number of output contacts
single pole single throw SPST
on-off switch
momentary on-off
push to make SPST
returns to normally open (off) when released
What is a magnetic field created through a current likely used to power In an aircraft
relay switches
what is a transformer
device to increase or decrease voltage in an AC circuit using electromagnetic induction
Advantages of relays
Can switch AC and DC
Can switch higher voltages
Often better for large currents
Can switch many contacts at once
disadvantages of relays
Big and heavy
Slow
Use more power
outside of strength, what’s a big difference between solenoids and relays
solenoids can be used for mechanical functions due to their moveable core
what is a wire
single strand
what is a cable
a collection of wire
skinny wires have a (higher or lower) number
higher
shielded wire
central wire carries signal, metallic shield (copper) connected to 0V
coaxial cable
designed to carry high frequency signals
two sets of wires in aviation typically use
terminal strips
what are the pros of connectors
smaller and lighter than terminal strips
immune to moisture, dirt, and vibration
is solder a wire
no it is a filler made of lead and tin
what was the first battery
voltaic pile
1799
Alessandro Volta
primary cell
non reversible reaction
not rechargeable
can produce current immediately on assembly
secondary cells
reversible reactions
designed for use, recharge
lower energy density than primary
good for high-drain application
wet cell
liquid electrolyte
must be vented as gas is produced
common dry cell has a nominal voltage of
1.5 volts
dry cell composition
anode = zinc cylindrical pot
cathode = carbon central rod
electrolyte = ammonium chloride paste
benefits of VRLA battery
low maintenance
does not require regular water addition
cannot spill
what is a Gell cell battery
“recominant battery”
creates oxygen in positive and hydrogen in negative to create water which prevents water loss
why do VRLA sometimes have a safety pressure relief valve
In case hydrogen production rate becomes too high
what modern batteries do aircraft use
secondary cell
24 volt lead
advantages of lead-acid batteries
less expensive
disadvantage of lead acid batteries
must be checked and replaced more often, less power to weight ratio
advantages of nickel cadmium batteries
greater power to weight ratio
CCV remains constant
How does a nickel cadmium battery look
several layers of anode ad cathode material rolled into a cylindrical shape
where are nickel cadmium batteries used
transport and commercial aircraft
disadvantage of nickel cadmium battery
near constant voltage makes it hard to detect low battery
downside of lithium ion batteries
prone to thermal runaway
upside of lithium ion batteries
best energy to weight ratio
no memory effect
operate at higher voltages
how do generators and alternators generate electricity
electromagnetic induction
wire rotates inside the magnet (or visa versa)
generator (alternator)
do generators produce AC or DC
AC
what is the armature
main current carrying electrical winding
receives induced voltage / current
what is the commutator
connects armature to generator
changes AC to DC
what are the brushes
electrical contacts which touch the commutator and provide a current path for the power to leave the rotating armature
rectifier
AC to DC
inverter
DC to AC
how are DC alternators similar to DC generators
change mechanical energy into electrical
produce electrical power through electromagnetic induction
produce AC and change it to DC
how do DC alternators create current
use field windings which are rotating driven by the engine
armature stationary
how do DC generators create current
permanent magnet field
armature windings are rotating
Alt vs Gen
alternator supplies power through direct contact
generator supplies power through commutator and brush assembly which makes an unreliable connection
Alt / Gen construction
armature - where voltage is produced
Field winding - creates magnetic field
rectifier - changes AC to DC
arrow side of the diode is (+ or -)
negative (where arrow is pointing)
why are alternators more reliable
needs less maintenance
technicians able to replace components
what does the voltage regulator do
controls field strength
keeps generator output at necessary voltage and current for variable load
series vs parallel circuit
series: constant current
parallel: voltage current
