Agenda Bell Work

• Notes: AC/DC and circuits

• Series vs. Parallel circuit Lab

• Bill Nye: Electricity

• Have HW out to be checked

• What is the relationship between current and voltage?

• Between current and resistance?

• Voltage and resistance?

AC/DC and circuitsAC/DC and circuitsNovember 19, 2012November 19, 2012

ObjectivesObjectives

1.1. Explain the difference between Explain the difference between alternating and direct currentalternating and direct current

2.2. Sketch a series and parallel circuit and Sketch a series and parallel circuit and list their applicationslist their applications

3.3. Recognize the function of circuit Recognize the function of circuit breakers and fuses.breakers and fuses.

Electric CurrentElectric Current

May be dc or acMay be dc or ac

Direct Current (dc)Direct Current (dc)

Made of electrons that flow in ONE Made of electrons that flow in ONE directiondirection

Battery produces dcBattery produces dc Move from the repelling negative terminal Move from the repelling negative terminal

to the attracting positive terminalto the attracting positive terminal

Electrons move slow, because they bump Electrons move slow, because they bump into other atoms in the wire – drift speedinto other atoms in the wire – drift speed

Alternating Current (ac)Alternating Current (ac)

Electrons in the circuit flow initially in one Electrons in the circuit flow initially in one direction and then in the opposite directiondirection and then in the opposite direction

Drift is zero – vibrate at about the same Drift is zero – vibrate at about the same position, don’t really travelposition, don’t really travel

Electricity that runs in some appliances Electricity that runs in some appliances and throughout your houseand throughout your house

Electric CircuitsElectric Circuits

Any path along Any path along which electrons which electrons can flowcan flow

For a steady For a steady current, there current, there must be no gapsmust be no gaps

Most circuits contain more than one device Most circuits contain more than one device that receives electric energythat receives electric energy

These devices are connected in one of These devices are connected in one of two ways – series or paralleltwo ways – series or parallel

Series CircuitSeries Circuit Current remains the Current remains the

same between each same between each devicedevice

Voltage decreases Voltage decreases through each devisethrough each devise

Resistance increasesResistance increases

This is the only path This is the only path for electronsfor electrons

If a break occurs anywhere the flow of If a break occurs anywhere the flow of electrons stopelectrons stop

Parallel CircuitsParallel Circuits

Devices are Devices are connected to the connected to the same two points in same two points in parallelparallel

Electrons leaving the Electrons leaving the battery travel through battery travel through one lamp and can one lamp and can return to the positive return to the positive terminalterminal

If you break one in the path you do not If you break one in the path you do not break the flow of charge to the other devicesbreak the flow of charge to the other devices

Houses are wired in parallelHouses are wired in parallel

Voltage remainsVoltage remains

the samethe same

Current increasesCurrent increases Resistance decreasesResistance decreases

OverloadingOverloading Circuits that carry more than a Circuits that carry more than a

safe amount of current – in safe amount of current – in parallel the more devices the parallel the more devices the less resistanceless resistance

To prevent overload fuses are To prevent overload fuses are connected to the circuitconnected to the circuit

It heats up and melts breaking It heats up and melts breaking the circuitthe circuit