Current Electricity Sections 2-2 & 2-3

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

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

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

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

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

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

SERIES AND PARALLEL CIRCUITS EXAMPLES