1. 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?

2. AC/DC and circuitsAC/DC and circuits
May 2, 2013May 2, 2013

3. ObjectivesObjectives
1.1. Explain the difference betweenExplain the difference between
alternating and direct currentalternating and direct current
2.2. Sketch a series and parallel circuit andSketch a series and parallel circuit and
list their applicationslist their applications
3.3. Recognize the function of circuitRecognize the function of circuit
breakers and fuses.breakers and fuses.

4. Electric CurrentElectric Current
 May be dc or acMay be dc or ac

5. Direct Current (dc)Direct Current (dc)
 Made of electrons that flow in ONEMade of electrons that flow in ONE
directiondirection
 Battery produces dcBattery produces dc
 Move from the repelling negative terminalMove from the repelling negative terminal
to the attracting positive terminalto the attracting positive terminal

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

8. Alternating Current (ac)Alternating Current (ac)
 Electrons in the circuit flow initially in oneElectrons 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 sameDrift is zero – vibrate at about the same
position, don’t really travelposition, don’t really travel
 Electricity that runs in some appliancesElectricity that runs in some appliances
and throughout your houseand throughout your house

9. Electric CircuitsElectric Circuits
 Any path alongAny path along
which electronswhich electrons
can flowcan flow
 For a steadyFor a steady
current, therecurrent, there
must be no gapsmust be no gaps

10.  Most circuits contain more than oneMost circuits contain more than one
device that receives electric energydevice that receives electric energy
 These devices are connected in one ofThese devices are connected in one of
two ways – series or paralleltwo ways – series or parallel

11. Series CircuitSeries Circuit
 Current starts theCurrent starts the
same between eachsame between each
devicedevice
 Voltage is dividedVoltage is divided
across all devicesacross all devices
 Resistance is theResistance is the
sum of all devicessum of all devices
 current goes down incurrent goes down in
each deviceeach device

12.  This is the only path for electronsThis is the only path for electrons
 If a break occurs anywhere the flow ofIf a break occurs anywhere the flow of
electrons stopelectrons stop

13. Parallel CircuitsParallel Circuits
 Devices areDevices are
connected to theconnected to the
same two points insame two points in
parallelparallel
 Electrons leaving theElectrons leaving the
battery travel throughbattery travel through
one lamp and canone lamp and can
return to the positivereturn to the positive
terminalterminal

14. • If you break one in the path you do not break the flowIf 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 inHouses are wired in
parallelparallel
 Voltage remainsVoltage remains
the samethe same
 Current is sum of all theCurrent is sum of all the
branchesbranches
 Resistance decreasesResistance decreases

15. OverloadingOverloading
 Circuits that carry more than aCircuits that carry more than a
safe amount of current – insafe amount of current – in
parallel the more devices theparallel the more devices the
less resistanceless resistance
 To prevent overload fuses areTo prevent overload fuses are
connected to the circuitconnected to the circuit
 It heats up and melts breakingIt heats up and melts breaking
the circuitthe circuit