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ELECTRICAL CIRCUITS
All you need to be an inventor is a good
imagination and a pile of junk.
-Thomas Edison
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What is it?
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• The movement
of electrons through a conductive material
What is it?
• Electrons bump into other electrons in adjacent shells (called
valence shells) and continue down the path
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Electrons will
only flow if there
is a complete
circuit for them
to flow around
• Electrons, which are negatively charged, emerge from the
negative terminal of the power supply
• Conventional notation, however, is to refer to the electricity as
emitting from the positive terminal of the power supply
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RESISTANCE CURRENT
How you should be
thinking about
electric circuits:
Voltage
the “speed”, and subsequent
force, that pushes the current
through the circuit
Water analogy
The higher the water fall the
more “voltage”
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VOLTAGE
CURRENT
How you should be
thinking about
electric circuits:
Resistance
friction that impedes flow of
current through the circuit
Water analogy
rocks in the river
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VOLTAGE RESISTANCE
How you should be
thinking about
electric circuits:
Current
The actual “substance” that is
flowing through the wires of the
circuit (electrons!)
Water analogy
The water molecules
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UNDERSTANDING
ELECTRICITY
• Air is conductive…if you have enough voltage to push
the electrons through it (i.e. – lightening)
• 10,000 volts might not hut you…but if it pushes just 1
amp of current through your heart it can be fatal
• If the circuit has no resistance, it’s called a short circuit
and infinite current will flow until the circuit fails (i.e. –
melts or depletes)
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Ohm’s Law
V=IxR
I = Current (Amperes) (amps)
V = Voltage (Volts)
Georg Simon Ohm (1787-1854)
R = Resistance (ohms)
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Ohm’s Law
V=IxR
• So more voltage will
provide you more current
Georg Simon Ohm (1787-1854)
• And more resistance will
provide you less current
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Simple Circuits
• Parallel circuit
– Many paths for
electricity
– 1 light goes out and the
others stay on
• Series circuit
– All in a row
– 1 path for electricity
– 1 light goes out and the
circuit is broken
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