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comes from the electrons in an atom when they are transfered them between objects.
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electrons have a negative (-) charge
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Static
Current Build-up of electrical charge Electrons move in non-specific directions
Flow of electricity through wires Electrons move in definite paths
Examples – lightning, zap from carpet when touch something, static cling in clothes and hair
Examples – anything with a cord or wire to power, hair dryer, phone, iPod
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Most objects tend to beMost objects tend to be
meaning that they have equal number of meaning that they have equal number of positive and negative charges.positive and negative charges.
# of Protons = # of Electrons# of Protons = # of Electrons(positive charge) = (negative charge)(positive charge) = (negative charge)
=
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Neutral Object Charged Object
-8+8
0
-6+10+4Net Charge: Net Charge:
Net Charge of Objects
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Opposite Charges Attract
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Same Charges Repel
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Law of Electrical Law of Electrical ChargesCharges
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2. Negative charges in the wall repel from the balloon.
1. Rub a balloon on a sweater to “charge it up.”
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3. The balloon sticks because the positive charges left over are attracted to the balloon.
Demonstration:Demonstration: How do Balloons stick to How do Balloons stick to
walls?walls?
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A battery uses chemical energy to move electrical charges.
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Circuits flow in a circular path from positive
end to negative end
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Light will not go onbecause the wire is
not connectednot connected to the battery;
no current will flow.no current will flow.
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Light bulb turns on because the electrical current can now flow through the complete circuit.
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• an accidental path for current to flow• often causing risk of shock or fire• a branch with zero or very low resistance
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Safety Devices
Circuit breaker - piece of metal that bends when it gets over heated opening switch because current is too high
Fuse - small piece of metal that melts if the current becomes too high opening switch
GFI (ground fault interrupter) - usually found in bathrooms or garages shuts off plug when current if too high.
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• Wire
• Power Source (1.5 V)
• Bulb
• Resistance
• Switch
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open closed
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WATCH!
Do you notice any difference between the wirings of the two circuits above?
Series CircuitsParallel Circuits
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Series Circuits
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The light bulbs turn on.
However, since the voltage drops, the lights are dimmer.
.75 V
.75 V
Battery is 1.5 V
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If this light bulb does not turn on,If this light bulb does not turn on,
neither light neither light bulb will turn bulb will turn on.on.
This is because the circuit is broken here;
so the current can’t flow to this bulb here.
Burned out light bulb
Battery is 1.5 V
Christmas lights were commonly made this way.
Series Circuits
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Current divides and Current divides and has more than one has more than one
path.path.
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Parallel Circuits
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The current divides because it has more than one The current divides because it has more than one path.path.
Even though the path is stopped, the other light turns on because its circuit is not broken.
Burned out light bulb
Your house is wired with parallel Your house is wired with parallel circuits.circuits.Why do you think this is so?Why do you think this is so?
Parallel Circuits
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… house was wired in series.
What would happen if a light bulb burned out?
How would you have to find out which one it was to
fix?
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Series Circuits Parallel CircuitsOnly 1 path for electricity to go
Many paths for electricity to travel
When 1 light in the path goes out, they all go out because there is no other path.
When 1 light in the path goes out the electricity can find another way to transfer the current
Current is the same in all points
Voltage is the same at each branch because each branch is like a separate series circuit connected to a source.
Voltage is reduce by each resistance added like another light bulb, heater, or appliance.
Each branch does NOT always have the same current because it depends on how much resistance is in each branch.Example: Saw has more than a lamp
