Transcript Electrical-Systems

Aircraft
Electrical
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
E
• Current (I) is the ‘amount’
of electrons flowing
• Measured in Amps
• Voltage (E) is the
‘pressure’ of the electrons
• Measured in Volts
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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)
b)
c)
d)
Protons
Neutrons
Electrons
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 socket
b) Battery
c) 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) Capacitance
b) Inductance
c) Resistance
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Question 4
• In a light bulb, the electrical resistance is in
the form of the:
a) Socket
b) Filament
c) Glass enclosure
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Question 5
• In an electrical circuit, the amount of electron
flow is measured by the:
a) Ammeter
b) Voltmeter
c) Loadmeter
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Question 6
• The pressure of the electron flow is measured
by the:
a)
b)
c)
d)
Ammeter
Voltmeter
Dosimeter
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 wiring
d) Prevent an electrical fire
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How much voltage does it take to kill a
person?
a) 15,000 volts
b) 120 volts
c) 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 circuit
d) All of the above
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