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Electricity
Electricity
All matter is made up of
positive charges and negative charges.
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The positives have mass
and are not usually free to move.
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Negative charges have no mass
and are free to move.
Negative charges move
through materials called conductors.
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Good Conductors do Not hold on to their
valence electrons well – ex. metals
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Negative charges are
attracted to positive charges
like mice are attracted to cheese.
Static Electricity
• Build up of Electrons creating Electric Charge
• Created By:
– Friction
– Induction
– Conduction
Until you get…
Static Discharge
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Anytime there is a natural attraction between two things
you can use it to make the objects do work.
The negative charges (mice) will gladly do work
in order to get to the positive charges (cheese).
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• Voltage:
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– The amount of work that each charge
(mouse) will do as it goes through the circuit.
– the amount of push on the charges or
– how hungry the mice are.
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• Resistance:
The opposition to the flow of charge (electrons).
Any appliance that asks the charge (mouse) to do
work will slow it down.
Resistance
• Decrease
• Increase
– Short wire
– Thick wire
– Cooler wire
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– Long wire
– Thin Wire
– Warm Wire
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• Current:
– The number of charges (mice)
passing a point per second.
The rate of flow of charges.
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D Battery
1.5 volts & 15 amps
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AA Battery
1.5 volts & 2.8 amps
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This set up has a voltage
(desire on the part of the mouse)
but no current flows because there is
no conductive path.
It has the ability to do work
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Circuits
• Series
• Parallel
– One Path for e-
– 2 or more Paths for e-
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Circuits
• Series
• Parallel
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– 2 or more Paths for e– Add Resistors then
Current Increases
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– One Path for e– Add Resistors then
Current Decreases
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Circuits
• Series
– One Path for e– Add Resistors then
Current Decreases
– Cells in Series
Increase Voltage
• Parallel
– 2 or more Paths for e– Add Resistors then
Current Increases
– Cells in Parallel
Longer Battery Life
Alternating Current
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120v
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One side of the outlet would change from
cheese to cat 60 times a second.
• Electrons move back and forth
• Produced by Power Plants
Direct Current
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• Electrons
move in one
direction
• From
negative to
positive
• Produced by
Batteries
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The battery goes "dead" when all the negative
charges make it through the circuit and get to
the positive charges.
Electromagnet
• Moving e- produce a magnetic field
– More coils / More strength
Electromagnet
• Moving e- produce a magnetic field
– More coils / More strength
– More current / More strength
Generators
• Electromagnetic Induction –
moving an coil of wire through a magnetic field
Generator
Changes
Mechanical Energy
to
Electrical Energy
Motor
• AC (alternating current) causes magnetic
poles to flip making the armature spin
Motor
Changes
Electrical Energy
To
Mechanical Energy