Transcript current electricity

CURRENT ELECTRICITY
Prentice Hall: Electricity and Magnetism
Chapter 2, Section 2
MRS. BRUNNER
SCIENCE
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I. Flow of Electric Charges
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A. What is Electric Current? (think of conveyer belt)
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1. continuous slow of electric charges through a material
2. static electricity does not flow (it builds up on an object) and can
not power devices
3. charges flow through a wire or similar material
4. rate of electric current – amount of charge that passes through a
wire in a given amount of time
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a. measured in ‘ampere,’ abbreviate as…
b. number of amps describes the amount of …
B. Current in a circuit (think of the race track)
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1. electric circuit – complete, unbroken path the electricity flows
through
2. charges flow from one place to another with no gaps on path
3. charges ‘flow’ – can be pushed or pulled through wire
4. circuits ‘begin and end’ at the place
5. there are circuits in every electrical device
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II. Conductors and insulators
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A. Conductors
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1. material through which electricity can easily flow
2. transfers charges well from one place to another
3. conduction electrons – electrons that are loosely connected
together and can flow easier, this is why a material is a conductor
4. what happens to electrons in a wire when you turn on a switch?
5. examples –
B. Insulators
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1. material through which electricity can not easily flow
2. electrons are…
3. examples –
4. Why don’t you get shocked when you touch an extension cord?
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III. Voltage
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A. Charges need energy to ‘flow’ in a circuit
B. The force that causes the ‘flow’ is called voltage
C. Potential energy – energy an object has as a result of it’s
position or height, energy is stored up in the object, remember
the roller coaster
 1. rollercoaster at top – has high potential energy
 2. roller coaster at the bottom - has low potential energy
 3. the difference in these 2 potential energies is called
potential difference (check out picture on pg. 49)
Electric current is present in a circuit b/c there is a difference in
electric potential energy between 2 places in the circuit and it is
the battery that causes this
Voltage causes the current in an electric circuit
Voltage source – a device that creates…
Voltage source examples -
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IV. Resistance (think of the pipe pictures)
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A. Current depends on resistance
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B. 4 Factors that determine resistance
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1. other things besides voltage can affect how electricity travels
through a circuit
2. resistance – measure of how difficult it is for charges to flow
through a circuit
3. the greater the resistance, the less current there is
4. Ohm – the unit used to measure how much resistance there is
5. symbol for Ohm –
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Path of least resistance
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1. if an electric charge can flow through either of 2 choices, …
2. How can the bird sit on the uninsulated wire?