Avionics Review - Ac Current

Front 1

Name 5 AC waveforms. Which is the most common?

Back 1

1) Sine Wave (Most common)

2) Square Wave

3) Triangle

4) Sawtooth

5) Rectangular

Front 2

What is the purpose of Electricity?

Back 2

To do work

Front 3

What is the primary function of DC electricity?

Back 3

To power the circuit

Front 4

What is one of the most important uses of AC electricity?

Back 4

To take the form of the information we process. AC adapts the information we want to send wirelessly across a long distance to the medium that will carry it. (a.k.a. the atmosphere for radio waves)

Front 5

What are 3 forms that AC signals can take?

Back 5

1) Voice

2) Digital data

3) Analog signals

Front 6

What are the 3 requirements of a communication system?

Back 6

1) Transmitter (Ex: Mickey's mouth)

2) Medium (Ex: air, the atmosphere)

3) Receiver (Ex: my ears, assuming I am still awake...)

Front 7

Describe the steps that occur when a DC powered radio sends a signal to another one.

Back 7

1) DC powers radio

2) Mic converts sound waves into AC current

3) Radio waves are transmitted

4) Another DC powered radio receives the signal

5) AC speaker converts AC signal back into sound waves

Front 8

Describe Direct Current

Back 8

1) Current only flows in one direction

2) Current and Voltage can change in magnitude, but not direction

3) Current flow is caused by a difference in potential (+ and -)

4) DC is capable of performing work

Front 9

What causes the difference of potential that drives DC electricity?

Back 9

Electrostatic forces, that is, the forces of attraction and repulsion between + and - charges.

Front 10

________ is required to perform work. The ________ provide the ________ that allows electricity to perform work.

Back 10

MASS,

ELECTRONS,

MASS

Front 11

How many valence electrons does an insulator have?

Back 11

>4 electrons

Front 12

How many e-'s does a semi-conductor have?

Back 12

exactly 4 e-'s

Front 13

How many e-'s does a conductor have?

Back 13

<4 e-'s

Front 14

What are the 3 requirements of a circuit?

Back 14

1) Source of current flow

2) Conductor to carry current

3) At least one Load to use current

Front 15

What is a Capacitor?

Back 15

A device used to store electrical energy in an Electro-static field. Composed of 2 conductors separated by an insulator

Front 16

What is an Inductor?

Back 16

A coil or device used to induce current in a conductor

Front 17

Which rule applies to Electron Flow Theory, the Left Hand Rule for coils, or the RIght Hand Rule for coils?

Back 17

Left Hand Rule for coils;

If fingers of left hand curl in direction of current flow in the coil, then the thumb indicates the North Pole of the magnetic field being generated

Front 18

What is Magnetism?

Back 18

The ability to attract materials containing Iron, and to influence e-'s

Front 19

What are the two types of Magnets?

Back 19

Permanent, Electromagnet

Front 20

What 7 things determine the strength of an electromagnet?

Back 20

1) Wire AWG

2) # of loops in coil

3) Size of loops in coil

4) Loop spacing

5) # of layers of loops

6) Core type

7) Amount of current flow

Front 21

Name the two types of Electrostatic Force

Back 21

1) Attraction (+ and -)

2) Repulsion (+ and+ or - and -)

Front 22

Define Voltage simply.

Back 22

A difference in potential between 2 unequal charges. Also called "Electromotive Force"

Front 23

What are the 4 characteristics of Electricity? What are their symbols? What are their units?

Back 23

1) Current (I), amps

2) Voltage (E), volts

3) Resistance (R), ohms

4) Power (P), Watts

Front 24

Define "Ampere"

Back 24

1 Coulomb of charge through a point in 1 second

Front 25

What is a "Coulomb?"

Back 25

6.28 Billion Billion electrons

Front 26

What is a "Volt?"

Back 26

Electrical pressure (EMF) required to push 1 Amp of current through 1 Ohm of resistance

Front 27

What is an "Ohm"

Back 27

The amount of resistance that limits current flow to 1 Amp under 1 Volt of pressure

Front 28

What is a "Watt" (and Who's on second?)

Back 28

The amount of power consumed when 1 Amp of current flows through 1 Ohm of resistance under 1 Volt of pressure

Front 29

What causes resistance? What does it produce?

Back 29

Friction, Heat

Front 30

Resistance _________ 'I', __________ 'V', and _________ 'P'.

Back 30

Opposes, Drops, Consumes

Front 31

Define "Power"

Back 31

A measure of the rate at which energy is used. It often takes the form of heat (whatever that means...)

Front 32

Name 3 effects that heat has on electrical components

Back 32

1) Changes their values

2) Changes their resistance

3) Causes them to fail

Front 33

What are the 3 failure modes? VERY briefly describe each one

Back 33

1) Catastrophic - "BOOM," the thing failed.

2) Latent - Should have taken better care of it... (shortened working life)

3) Intermittent - It's a very on-again, off-again kind of relationship.

Front 34

Give the equations for Ohm's Laws

Back 34

E = I x R

P = I x E

Front 35

What determines the type of circuit that a circuit is, or chooses to be if it wasn't born that way?

Back 35

The number of different paths for current

Front 36

What determines the resistance of a conductor?

Back 36

1) AWG (cross-sectional area)

2) Length

3) Material (Al or Cu on aircraft)

4) Temperature (T and R are directly proportional)

Front 37

Name 4 benefits of the Single Wire Method used in aircraft

Back 37

1) Cost savings

2) Weight savings

3) Space savings

4) Less electromagnetic/radio frequency interference

Front 38

What special equation can be used for Parallel circuits if the resistance in ALL Branches is the SAME?

Back 38

Front 39

What special equation can be used for Parallel circuits if there are ONLY 2 Branches?

Back 39

Front 40

Why is AC current used more and more in aircraft? (4 reasons)

Back 40

1) It is easier to produce in large quantities

2) AC values are easier to change (current, voltage)

3) Requires smaller components

4) Savings in Weight, Space, and Cost

Front 41

What 3 things are required in order to produce AC using Magnetism?

Back 41

1) Motion

2) Conductor

3) Magnetic Field

Front 42

Define "Induction"

Back 42

The wireless transfer of energy

Front 43

When using the term "AC," it can be assumed that the ___________ __________ is being referred to.

Back 43

Effective Value

Front 44

Average Value = ?

Back 44

Average Value = 0.637 x Peak Value

Front 45

Which value of AC is considered to be the Most Important value?

Back 45

Effective Value

Front 46

What is another name for the Effective Value?

Back 46

Root-Mean-Squared value

Front 47

Describe the Effective Value

Back 47

1) It can be compared to DC by the amount of work it can perform

2) EV = 0.707 x Peak Value (70.7% of PV)

3) EV is the value that is MEASURED by multimeter or other equipment

Front 48

AC Peak = ?

AC Peak - Peak = ?

Back 48

AC peak = 1/2 of Peak - Peak value

or = 1.41 x RMS

AC Peak - Peak = 2x Peak value

Front 49

Define "Frequency" for AC

Back 49

# of cycles of AC per second. Measured in Hertz (Hz)

Front 50

What is a "Hertz?"

Back 50

1 Hertz (Hz) = 1 AC cycle in one second

Front 51

What is the most common Frequency in Aircraft AC systems?

Back 51

400 Hz

Front 52

Define "Period"

Back 52

Time required for one cycle of AC to occur (in seconds, mSec, uSec, etc.)

Front 53

What is "True Power?"

Back 53

Power value that takes into account Phase Shift, and is the actual amount of Power available for use.

Front 54

What is "Apparent Power?"

Back 54

AP = Effective 'E' x Effective 'I'

Does NOT take into account Phase Shift

IS expressed in VOLT-AMPS (VA) instead of watts

Front 55

What is the "Power Factor?"

Back 55

1) The amount of 'I' that is IN PHASE with the 'E'

2) Ratio between True Power and Apparent Power

3) When 'E' and 'I' are in phase, PF = 1.0

4) PF = cos(phase angle) when 'I' and 'E' are NOT in phase

5) When PF = 1.0, True Power = Apparent Power

Front 56

What is "Impedence?"

Back 56

The total opposition to the flow of current.

(Resistance + Reactance)

Symbol = Z

Front 57

What is "Reactance?"

Back 57

The opposition to the flow of current from Inductance or Capacitance. Total reactance is the sum of these two. (Symbol for reactance = X)

Front 58

Give the equation for Ohm's Law for AC

Back 58

Front 59

Give the equation for Inductive Reactance

Back 59

Front 60

Give the equation for Capacitive Reactance

Back 60

Front 61

Give the equation for Total Reactance

Back 61

Front 62

Give the equation for Impedence

Back 62

Front 63

Give the equation for Apparent Power

Back 63

Front 64

Give the equation for True Power

Back 64

Front 65

Give the equation for Power Factor

Back 65