CAP 1 TO 5

Question 1

DEFINITIONS OF ANYTHING THAT USES ELECTRICITY? (FOR REGULATORS)

Answer 1

COMPONENTS
LOAD
CONSUMER
RESISTIVE LOAD

Question 2

WHAT IS THE IMPEDIANCE?

Answer 2

AC RESISTANCE.

DC USES ONLY RESISTANCE

Question 3

WHAT IS INDUCTANCE?

Answer 3

THE GENERATION OF ELECTRICAL FLOW USING MAGNETS

Question 4

REACTANCE?

Answer 4

The resultant effect of INDUCTANCE or CAPACITANCE

Question 5

CAPACITANCE?

Answer 5

The ability to store a charge or electricity

Question 6

Describe a/c electrics type?(light,twin,commercial and new wide bodies)

Answer 6

Light : 14 (12)V DC Like c152

Light twin: 28 (24) V DC (some have inverter for ac avionics) like DA42

Jets : 115/200 V 400Hz 3 phase AC , 28V (24)V DC
Like 737,a320

787/a350: larger voltage sys 1600V

Question 7

Convention current flow in aviation?

Answer 7

From POSITIVE TO NEGATIVE

Even tho the real electron flow is from neg to pos

Question 8

Voltage symbols?

Answer 8

V, PD , E , EMC , U

Question 9

Ohms LAW equation?

POWER equation?

Answer 9

Ohms law: V = I x R

POWER : V x I or I (squared) x R

Question 10

Mutual inductance?

Answer 10

When in a conductor there is a flow of electrons an EMF is created which can interfere with other cables

Question 11

Faradays law ?

Answer 11

States that when ever there is a movement of a conductor around a magnetic field we get an EMF which creates electricity.

The strength depends by:
Cable length
Field strength
Since angle (theta) 90 degree max to the fieild
Speed of the conductor

Question 12

Lorenzes law?

Answer 12

The Lorentz force law states that a magnetic field exerts a force on a moving current.The Hall effect further states that when a magnetic field is placed perpendicular to the direction of flow of an electric current, it will tend to deflect and separate the charged ions.

Question 13

The advantages of bonding parts of a/c?

Answer 13

Ensure low resistance patch to static wicks

Unifirm electrical potential (not to make V=0 but to have an even distribution of V)

Prevents radio interfernce

Question 14

primary and secondary battery differences?

Answer 14

Primary cells : can’t be recharged

Secondary : can be racharged

Question 15

Basic of batteries:

Answer 15

Provide power to start engine or apu

Short time power supply (30min) in emergency

Question 16

What is the Nominal voltage?

Answer 16

Is the nominal benchmark voltage.

When engines are running nominal V is higher

Question 17

Lead acid battery characteristics?

Answer 17

@12,5 -12,7 v OFF LOAD (not connected to anything)
@13,3-14,4 V under charging conditions
@When 11,2 V is reached becomes unstable
@2,2 V per cell
@Higher discharged rate
@ a 12 v battery has 6 cells
@electrolite may boil off emitting flammable gas
@negatively affected by temp, and has a lower cell V when placed onload

So not good as Nicd or lithium

Question 18

Nicd battery characteristics?

Answer 18

@1.2 V to 1.25 V nominal voltage
@lower discharged rate
@longer life and do not give off gases whilst chargin
@ more robust
@higher energy density
@Voltage remains constant over almost discharge cycle
@expensive
@thermal runaway
@very significant negative temperature coefficient (as the temp rises ,internal resistance falls,this pose a charging problem risk.
@suffer from memory effect
Compostions:
Postive plate nickel hydroxide
Negative plate calldmium hydroxide 
Electrolite 70% distilled water 30% potassium hydroxide
12v battery contains 10 cells
24v contains 20 cells

Question 19

Lithium batteries?

Answer 19

@12-24 nominal V
@3.6 V per cell
@ usually encased in a container for safety
@between each cells ceramic plates give protection in case of thermal runaway
@thermal runaway
@ good energy weight ration compared to lead batteries
@less time to charge
@keeps correct voltage for much longer under load

Question 20

Why a higher nominal voltage is required in all batteries ?

Answer 20

To charged them up above their nominal voltage value ,because there are some losses due to resistance.

Question 21

Connections methods of circuits V/I ?

Answer 21

In series voltage adds up and current the same

In parallel CURRENT adds up voltage the same

Question 22

What is a Relay ?

Answer 22

A device which can operate high voltage circuits with a small current

Question 23

Solenoid ?

Answer 23

Physically move a bar against a spring pressure to turn on or off circuits

Question 24

Charging process for the 3 batteries type?

Answer 24

Nicd and Li-On batteries a dedicated controller will monitor V,I and temp

In Lead acid batt. the charger will recharge using three distinct stages : BULK ,FLOAT and ABSORPTION

During charging off gassing with lead batteries can take place.
And with Nicd /lithium thermal runaway can take place.

Under normnal circumstances 20 min is the time to fully recharge a batt.

Question 25

What to do in case of Thermal runaway?

Answer 25

Biggest issue with modern batteries
The BCL ( battery charger limiter) are the controllers which will monitor the variables and charge the battery accordingly.but an increase in charging current may trigger thermal runaway.
In case of fire >> cool down battery and starve oxg supply.(halon extinguishers are very effective for battery fires)
On lithium batteries it can take place  for external heating ,over charging ,under charging,high current charging,structural damage.

Question 26

Two types of lithium batttery and compositions?

Answer 26

Lithium ion and lithium polymer

Ion uses liquid electrolyte whereas the polymer uses dry solid electrolyte.
Polymer is more robust.