AircraftElectrical Systems

Ted Spitzmiller

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C-182T Electrical System

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What is Electricity?

• Flow of electrons from one atom to another

+-

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Like a bucket brigade

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Where do we get ‘positive 'attraction—from a battery…

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Putting some ‘resistance’ into the flow provides useful ‘work’

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‘Current’ flows in the opposite direction to the electrons

• Voltage (E) is the ‘pressure’ of the electrons

• Measured in Volts

• Current (I) is the ‘amount’ of electrons flowing

• Measured in AmpsE

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Moving a coil in a magnet generates electricity to recharge the battery

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Two types of ‘current’

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Why is Electricity Dangerous• Minimum current a human can feel depends on

current type (AC or DC) and freq. – 1 mA of AC at 60 Hz (1/1000 of an amp)– 5 mA for DC.

• High current can cause tissue damage or fibrillation (cardiac arrest)– 60 mA of AC (rms, 60 Hz) – 300–500 mA of DC

• AC at 120 V, 60 Hz is an especially dangerous because it usually exceeds the let-go threshold

• Seriousness of the shock depends on current path through the body Ohms law E=IR

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Quiz time

• Electricity is the ‘flow’ of:a) Protonsb) Neutronsc) Electronsd) Klingons

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Question 2

• In a DC circuit, the positive force used to make the current flow is often obtained from:a) Wall socketb) Batteryc) Alternator

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Question 3

• To keep a battery from depleting its ‘charge’, rapidly (and perhaps burning up) each item to be powered must provide some form of electrical:a) Capacitanceb) Inductancec) Resistance

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Question 4

• In a light bulb, the electrical resistance is in the form of the:a) Socketb) Filamentc) Glass enclosure

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Question 5

• In an electrical circuit, the amount of electron flow is measured by the:a) Ammeterb) Voltmeterc) Loadmeter

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Question 6

• The pressure of the electron flow is measured by the:a) Ammeterb) Voltmeterc) Dosimeterd) Parkingmeter

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Question 7

• The purpose of a circuit breaker is to:a) Sense current that may be too high for the

circuit.b) Interrupt the flow of electricity to the ‘load’c) Protect the airplane’s electrical wiringd) Prevent an electrical fire

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How much voltage does it take to kill a person?

a) 15,000 voltsb) 120 voltsc) While voltage may be a factor, as little as 30

ma of current can cause ventricular fibrillation..

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What is a ‘short circuit’?

a) A direct path from a ‘ground’ to the positive source of power

b) A abnormal low resistance connection c) A possible destructive condition in an

electrical circuitd) All of the above

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