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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?• The movement of electrons through a conductive material• Electrons bump into other electrons in adjacent shells (called
valence shells) and continue down the path
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• 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
Electrons will only flow if there
is a complete circuit for them to flow around
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How you should be thinking about electric circuits:
Voltagethe “speed”, and subsequent force, that pushes the current through the circuitWater analogyThe higher the water fall the more “voltage”
VOLTAGE RESISTANCE CURRENT
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How you should be thinking about electric circuits:
Resistancefriction that impedes flow of current through the circuitWater analogyrocks in the river
VOLTAGE RESISTANCE CURRENT
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How you should be thinking about electric circuits:
CurrentThe actual “substance” that is flowing through the wires of the circuit (electrons!)Water analogyThe water molecules
VOLTAGE RESISTANCE CURRENT
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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 = I x R
Georg Simon Ohm (1787-1854)
I = Current (Amperes) (amps)
V = Voltage (Volts)
R = Resistance (ohms)
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Ohm’s Law
V = I x R
Georg Simon Ohm (1787-1854)
• So more voltage will provide you more current
• And more resistance will provide you less current
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Simple Circuits
• Series circuit– All in a row– 1 path for electricity– 1 light goes out and the
circuit is broken
• Parallel circuit– Many paths for
electricity– 1 light goes out and the
others stay on
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Measuring current
A A
This is how we draw an ammeter in a circuit.
SERIES CIRCUIT PARALLEL CIRCUIT
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Measuring currentSERIES CIRCUIT
PARALLEL CIRCUIT
• Current is the same at all points in the circuit.
2A 2A
2A
• Current is shared between the components
2A2A
1A
1A
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Measuring voltage
V
This is how we draw a voltmeter in a circuit.
SERIES CIRCUIT PARALLEL CIRCUITV
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3V
Series Circuit
Voltage is shared between the components
3V
6V
Measuring voltage
Like a train running through brick walls
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Parallel Circuit
Voltage is the same in all parts of the circuit.
3V
3V
3V
Like two people under the same waterfall
Measuring voltage
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