Download current electricity notes

Sections 2-2 & 2-3
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Def: The flow of electrons through a circuit
Parts of an Electric Circuit
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Source & Sink – where e- start and finish the circuit
 Difference in charge creates voltage to drive the e- through
the circuit
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Path
 Must be complete with no breaks from source to sink
 Conductor – passes e- easily
 Insulator – holds e- tightly so they are unable to flow
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Switch – turns electricity in circuit on or off
 Open – off
 Closed - on
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Resistor – any device that uses the electricity
Ways to measure current electricity
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Voltage (V) – potential difference between the source
and sink
 How positive one terminal is compared to how negative the
other is
 Pushes/pulls e- through circuit
 Volts
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Current (I) – the amount of electrical charges flowing
per unit of time
 Amps
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Resistance (R) – the opposition to flow of electric
charges
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Ohms
Path of least resistance
Larger wires: less resistance
More paths: less resistance
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Mathematical relationship between current,
voltage and resistance
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R = V/I
I = V/R
V=IXR
Increase Voltage: Increase Current
Increase Resistance: Decrease Current
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Series Circuit – single path
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Parallel – multiple paths
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More resistors: decrease current
Any break in circuit, entire circuit goes off
More paths  increase current
A break in one path does not mean entire circuit
shuts off
Key: for electricity to flow, e- must be able to
go from source to sink without going across a
break
EXAMPLES
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Short Circuit –
electricity that takes an
unintended path
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Third Prong – ground
wire
 Directs short circuits into
the ground
 Keeps it from shocking
you
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Lightning rod – directs
electric current from
lightning into the
ground
Fuse – prevents too
much current by
burning a strip 
breaks circuit
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Must replace fuse
Circuit Breaker –
prevents too much
current by switching off
the circuit
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Uses electromagnetism
Can reset switch
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Electricity is generated at the power plant
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Power – the rate at which electricity is used
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Electromagnetic Induction
Step-up Transformer – increases voltage for long
distance
Step-down transformer – decreases voltage for safer
transmission to homes
Voltage X Current
watts or kilowatts
Energy – how much electricity is used
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Power X Time
Kilowatt-hours