This document explains the differences between alternating current (AC) and direct current (DC). It defines AC as an electric current that periodically reverses direction and changes its magnitude continuously with time in contrast to DC, which flows in one direction. The document also outlines the key characteristics of series and parallel electric circuits. Series circuits have the same current flowing through all elements and the total voltage is divided among the elements. Parallel circuits have the same voltage across each element and the total current is the sum of the currents in the individual branches. The document concludes by noting that fuses are used to prevent circuit overloading by melting and breaking the circuit if too much current passes through.

1. AC/DC and circuitsAC/DC and circuits
April 17, 2015April 17, 2015

2. 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.

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

4. 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

6.  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

7. 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

8. 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

9.  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

10. Series CircuitSeries Circuit
 Current is the sameCurrent is the same
throughoutthroughout
 Voltage is dividedVoltage is divided
across all devicesacross all devices
 Resistance is theResistance is the
sum of all devicessum of all devices

11.  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

12. 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

13. • 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 is dividedResistance is divided
across each deviceacross each device

14. 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