ELECTRICITY TEST AAAAAA

a changing magnetic field will generate a ________

current

voltage is greatest when the magnetic flux through the coil changes the fastest (T/F)

true dat

in DC, positive is what color?

red

in DC, negative is what color?

black

in AC, voltage (hot) is what color?

black

in AC, neutral (voltage return) is what color?

white

in AC, ground is what color?

green

what is needed to make a basic AC generator?

coil of wire, a magnet, movement between magnet and coil and a complete circuit/load

if you added more coils to an AC generator, what are some drawbacks?

generates more heat, more expensive, it's heavier, requires more space, wastes more energy and needs to cool more

if you added a stronger magnet to an AC generator, what are some drawbacks?

more expensive, more friction/heat, heavier, counter EMF (interfere with radios), more vibration, wares faster, more momentum required/needs to spin faster (gears/pulleys)

if the amount of wire in the stator/coil is doubled then the voltage via electromagnetic induction...

doubles, silly

_______ as applied to AC is the number of cycles per second

frequency

where does the rotation spin come from for an AC generator?

the engine rotation, duh

all alternators have a safety function. What is it? what's it do?

a belt. it'll break and stop the alternator from destroying the engine

How does a powerplant work?

we burn coal. it heats up water. steam turns turbine. it spin. it spin generator or alternator. then it condenses and does it all over again. no water is lost or gained. yay electricity.

how do nuclear powerplants work?

reactor splits uranium atom apart. shit heats up and heats up water. steam make turbine spin. turbine spin generator or alternator. boom electricity

a rectifier converts ___ to ____

AC to DC

a _____ is a device that limits voltage/current flow to only 1 direction

diode

what's LED stand for?

light emitting diode, stupid shit

What's forward bias

current flows easily, diode acts like a closed switch

what the heck is reverse bias

minimal current flow, diode acts like an open switch

can you overpower a diode?

yea it go boom

is sea water a good conductor?

yuh it got salt

in a full wave rectifier, VDC polarity is not constant (T/F)

false, it is

how can there be current flow but 0 voltage?

voltage is electrical potential, current is the amount of electrons

what happens if a diode isn't sized accordingly?

bOOM

if a diode go boom and welds together, what happens?

it's a short

three phase half wave needs how many diodes?

three

three phase full wave produces the best DC (T/F)

true dat

rotational energy in, electrical energy out is a what?

alternator

electrical energy in, rotational energy out is a what?

motor brrrrr

a changing current will generate a _____

magnetic field

what are the four wave thingies?

half wave three phase, half wave single phase, full wave single phase, full wave three phase

what do alternators power in light aircraft?

lights, instruments, radios and electrical equipment

electrical power used in the aircraft comes from the fuel (T/F)

true, also the battery

fun fact a 737 or A380's fuel cost $5,000 per hour

it might be a bonus question

the less power an alternator generates the greater the fuel burn (T/F)

false, more

if the alternator fails, the piston engine will continue to operate but you'll lose power in the cockpit but not right away because you still have the battery (T/F)

true

alternator powers the spark plugs (T/F)

false

the alternator rotates faster than the engine because of the faster changing magnetic field which produces more power (T/F)

true

in large aircraft, the alternator uses a combo of AC and DC (T/F)

true

in large aircraft, we use 28 VDC to charge the battery (T/F)

yup true

for each revolution of the alternator, the unit produces three separate voltages and the sine waves for these voltages are separated by 90 degrees and they're designed to be brushless

false, it's 120 degrees (but everything else is right)

what's a CSD?

regulates the speed of the AC generators produce 400 hz

faster rotation = higher frequency (T/F)

true

the alternator needs to spin at a constant speed to produce 400 hz (T/F)

true

the CSD stands for?

constant speed drive

no CSD needed on APU since APU operates at constant speed (T/F)

true

what does IDG stand for?

integrated drive generator

what's the IDG

a combo of the generator and the CSD

some aircraft have a starter generator that initially starts the engine (T/F)

true

what is the RAT (ram air turbine) used for?

small emergency generator on the fuselage and it's a source of electrical and hydraulic power. it automatically deploys at activates. uses airspeed to spin a propeller

kVA = kW x Pf (T/F)

false, kW = kVA x Pf

the schematic symbol for a diode looks like a fast forward button (T/F)

true. the way I remember it is when you fast forward a movie it's going one way

impedance is abbreviated as the letter _________

Z

resistance doesn't change when you're finding the impedance in an AC circuit (T/F)

true. remember that one slide where everything was 15

what's the formula to find power?

P=IE. easy as pie.

What do capacitors do?

they store energy in an electroSTATIC field and you can release it sometime later

are capacitors solid state?

yes, although Dr. Kozak was like that's debatable because that one kid in class wanted to question it because he wants to make our lives more complicated

what's a capacitor schematic symbol look like?

a pause button with two lines on the sides

what is capacitance measured in?

farads

are farads a lot of energy?

yes, big big energy

describe a capacitor construction

two plates with an insulating material in the middle

in an uncharged capacitor, both plates have a(n) ________ number of electrons

equal. fun fact they are electrically neutral

what happens when a capacitor is charged?

one plate is supplied with an excess of electrons and is therefore negatively charged. the electrons were removed from the other plate so that one is positively charged

what happens when a capacitor is charging?

an electric field is set up between the plates. the more it charges the stronger the field. the electrical energy stored is contained in the electrical field and shows up as voltage across the plate. wowie.

a capacitor is limited by____

dielectric material (the insulating material), the distance between plates and the material of the plates

what does WVDC stand for?

working voltage direct current

capacitors are rated 50% higher than what is expected in the circuit (T/F)

true

capacitors can't put out more energy than they receive (T/F)

true

the farther the plates are in a capacitor, the weaker the electrostatic field but if the plates touch then it's a short (T/F)

true

to find XC the formula is XC = 1 / 2πFC (T/F)

troo

frequency goes up as ________ goes down

resistance

while charging a capacitor with DC, when the switch is open no current flows in the circuit and the capacitor doesn't change (T/F)

true

a capacitor charges until the voltage buildup across it does not equal the applied voltage (T/F)

false it does

how do variable capacitors work?

changing the rotation of the plates using a dial

capacitors smooth out the peaks and valleys of a three phase full wave and lowers the voltage a little bit (T/F)

troo :)

if you increase frequency, the capacitor must charge in less time (T/F)

t r u e

capacitors block _________

car radios

increase capacitance = current increases (T/F)

true

what offers opposition to current flow in an AC circuit?

resistance (resistor/power user), capacitive reactance (capacitors), inductive reactance (inductors)

is the total capacitance less than that of any individual capacitor in series?

yuh

what is the formula for C total in series?

C total = 1 / 1/c1 + 1/c2 + 1/c3

is the total capacitance greater than any individual capacitor in parallel?

yas

what is the formula for C total in parallel?

C total = c1 +c2...

do capacitors in parallel act as a single capacitor with a separation between their plates equal to the sum of the separation of the individual capacitors?

no it's series

for current to flow, voltage in a circuit has to be greater than .5V (diode slides) (T/F)

false, .7

full wave rectifiers use ______ diodes to cut the AC wave in half and flip the negative side

4

in a full wave rectifier, current can only flow ______ to ________

+ to -

the diode redirects the bottom half of the wave to the top (T/F)

true