Download - Ac dc and circuits
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 circuitsMay 2, 2013May 2, 2013
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 starts the Current starts the
same between each same between each devicedevice
Voltage is divided Voltage is divided across all devicesacross all devices
Resistance is the Resistance is the sum of all devicessum of all devices
current goes down in current goes down in each deviceeach device
This is the only path for electronsThis is the only path for 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 break the flow If you break one in the path you do not break the flow of charge to the other devicesof charge to the other devices
Houses are wired in Houses are wired in parallelparallel
Voltage remainsVoltage remains
the samethe same
Current is sum of all the Current is sum of all the branchesbranches
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