1. Current Electricity
Sections 2-2 & 2-3

2. CURRENT ELECTRICITY Def: The flow of electrons through a circuit
Parts of an Electric Circuit
Source & Sink – where e- start and finish the circuit
Difference in charge creates voltage to drive the e- through the circuit
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
Switch – turns electricity in circuit on or off
Open – off
Closed - on
Resistor – any device that uses the electricity

4. CURRENT ELECTRICITY Ways to measure current electricity
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
Current (I) – the amount of electrical charges flowing per unit of time
Amps
Resistance (R) – the opposition to flow of electric charges
Ohms
Path of least resistance
Larger wires: less resistance
More paths: less resistance

5. OHM’S LAW
Mathematical relationship between current, voltage and resistance
R = V/I
I = V/R
V = I X R
Increase Voltage: Increase Current
Increase Resistance: Decrease Current

6. SERIES AND PARALLEL CIRCUITS
Series Circuit – single path
More resistors: decrease current
Any break in circuit, entire circuit goes off
Parallel – multiple paths
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

7. Electrical Safety
Short Circuit – electricity that takes an unintended path
Third Prong – ground wire
Directs short circuits into the ground
Keeps it from shocking you
Lightning rod – directs electric current from lightning into the ground
Fuse – prevents too much current by burning a strip  breaks circuit
Must replace fuse
Circuit Breaker – prevents too much current by switching off the circuit
Uses electromagnetism
Can reset switch

8. What you pay for? Electricity is generated at the power plant
Electromagnetic Induction
Step-up Transformer – increases voltage for long distance
Step-down transformer – decreases voltage for safer transmission to homes
Power – the rate at which electricity is used
Voltage X Current
watts or kilowatts
Energy – how much electricity is used
Power X Time
Kilowatt-hours

10. SERIES AND PARALLEL CIRCUITS EXAMPLES