Systems 1 DC Circuits
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Resistance in relation to Temp, Length, and cross sectional area of the conductor.
- Proportional to Temp and Length
- Inversely proportional to Cross sectional area
State Ohms law
V = IR
Voltage = Amps x Resistance.
State both equations for Power
P = VI
P = I2 R
State Kirchoffs Law
I1 = I2 + I3
Primary and Secondary cells are also known as what?
Primary - non Rechargeable
Secondary - Rechargeable
In an Primary (Dry) Cell, what are the positive core, Negative case, and electrolyte made of?
Positive - Carbon
Negative - Zinc
Electrolyte - Ammonia Chloride paste
In an Secondary Cell, what are the positive core, Negative case, and electrolyte made of?
Positive plates of Lead Peroxide
Negative plates of Lead
Dilute Sulphuric Acid
How many volts will a Lead Acid Cell produce?
2.1 volts max
How long is the standard discharge period when testing the capacity of batteries?
How long should a voltmeter show the rated voltage of the battery when a test load is put in parallel if the battery is healthy?
Should show rated voltage for 15sec
What should the SG range be in a fully charged lead acid battery?
What will SG be when fully discharged?
Charged 1.25 - 1.30
In an Alkaline NiCad Battery what are the positive and negative plates, and the Electrolyte made of?
Positive - Nickel Hydroxide
Negative - Cadmium Hydroxide
electrolyte - Distilled water and potassium Hydroxide
Advantages of NiCad over Lead Acid
Smaller, Lighter, more Robust
Last Longer (more charge-discharge cycles)
Better performance at low temps
voltage remains constant through whole discharge cycle
Can be left fully discharged
How many volts per cell do Nicads produce?
Disadvantages of Lead Acid Batteries
Give off Oxygen and Hydrogen while being charged
Cant be left in a discharged state or lead sulphate coats the plates and stops charge being accepted
disadvantages of Nicad batteries
Low thermal capacity so prone to thermal runaway when being charged
When connecting batteries in Series, what happens to the rated capacity, and to the voltage
Rated Capacity remains the same
voltages are summed
When connecting batteries in Parallel, what happens to the rated capacity, and to the voltage
Rated Capacity is summed
Voltage remains same as for a single battery
How is the ground power relay powered from the 3 pin receptacle?
From the shorter of 3 pins so it cuts power before the other 2 longer pins come out and cause possible arcing
Name the 3 typical requirements of an aircraft electrical system
1) Supply to all equipment must be maintained unless total demand exceeds available supply
2) Systems faults should have the least possible effect on overall system functioning
3) A fault on one piece of equipment should not affect the power supply to the others
What are Vital consumers?
Services required in an emergency when all main power sources are lost. Emergency lighting, fire detection etc. Connected Directly to battery supply
What are essential consumers?
Necessary for safe flight in an emergency situation. Connected to bus bar than can be supplied by Gen or Batt
what are Non-Essential consumers?
Can be safely disconnected during in-flight emergency for purposes of load shedding. Supplied from the Gen bus
At what voltage will over-volt protections typically kick in with a 12v system?
How many degrees of motion does a rotary actuator typically move through?
fuel cocks, hydraulic rotary valves, butterfly valves etc
What is the active component of a circuit breaker, and what is a difference between "trip-free" and "non trip-free"
Trip-free cant be held in to make the circuit
Static wicks are made of what
Carbon or Copper
What is the bonding component in conducting tyres
Carbon - normally only nosewheel
What re-fueling flow rate could produce static electricity
5000l/min or more.
In over wing refueling nozzle must touch airframe as fuel exciting can cause spark.
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