Electric CircuitsElectric Circuits

Goals: electricity, voltage, current, Goals: electricity, voltage, current, resistance, ohm’s law, Kirchoff’s resistance, ohm’s law, Kirchoff’s

laws, power and energy laws, power and energy

ElectricityElectricity

Electricity – flow of electrons or……… Electricity – flow of electrons or………

the flow of electric chargethe flow of electric charge

One of the six forms of energy: cause a change One of the six forms of energy: cause a change or do workor do work

W = F x d Nm JW = F x d Nm J

Circuit – pathway for electronsCircuit – pathway for electrons

parts include: wire, battery (source), loads, parts include: wire, battery (source), loads, resistors and a switch that……….resistors and a switch that……….

Opens and Closes the circuitOpens and Closes the circuit

Current and VoltageCurrent and Voltage

Current – the movement of electric chargeCurrent – the movement of electric chargeSymbol “I” Measured in amps, flashlight is Symbol “I” Measured in amps, flashlight is about 1/2 ampabout 1/2 ampMeasured with an ammeterMeasured with an ammeterVoltage – electrical potential or potential Voltage – electrical potential or potential difference that causes the flow of chargedifference that causes the flow of chargeEnergy supplied by moving chargeEnergy supplied by moving chargeSymbol “V” measured in voltsSymbol “V” measured in voltsMeasured with a voltmeter each cell = 1.5 vMeasured with a voltmeter each cell = 1.5 vBatteries are cells connected in series Batteries are cells connected in series

Resistance and Ohm’s LawResistance and Ohm’s Law

Resistance – the opposition to flowResistance – the opposition to flow

Varies with each load: blow drier vs bulbVaries with each load: blow drier vs bulb

Symbol R or “Symbol R or “Ω” measured in ohmsΩ” measured in ohms

Resistors control flow in circuits Fixed or Resistors control flow in circuits Fixed or Variable (potentiometers)Variable (potentiometers)

Measured with a ohmmeter Measured with a ohmmeter

Ohm’s Law relates voltage, current and Ohm’s Law relates voltage, current and resistanceresistance

V = I RV = I R

Series CircuitsSeries Circuits

Series – all loads are on one pathwaySeries – all loads are on one pathwayOne load can open the circuitOne load can open the circuitCurrent remains the same on each loadCurrent remains the same on each loadTotal Resistance is the sum total of each resistor Total Resistance is the sum total of each resistor or load or load There is a voltage drop across each loadThere is a voltage drop across each loadTotal Voltage at the source is the sum of all Total Voltage at the source is the sum of all voltage drops Kirchoff’s voltage lawvoltage drops Kirchoff’s voltage lawProblems – add Rs to get total, use total V and Problems – add Rs to get total, use total V and total R to calculate each voltage droptotal R to calculate each voltage drop

Parallel CircuitsParallel Circuits

Parallel circuits have an alternate pathway for electrons Parallel circuits have an alternate pathway for electrons Branch CircuitBranch CircuitCurrent entering a branch must exit Kirchoff’s current Current entering a branch must exit Kirchoff’s current lawlawVoltage stays the same across each branch Voltage stays the same across each branch advantage of its use household circuits each branch advantage of its use household circuits each branch can be opened independently can be opened independently since each branch has the same voltage, the current since each branch has the same voltage, the current can be calculated independently by knowing the can be calculated independently by knowing the resistance and resistances totaledresistance and resistances totaledShort CircuitShort Circuit

Electrical Power and EnergyElectrical Power and EnergyPower – the rate at which work is done or energy Power – the rate at which work is done or energy converted to another formconverted to another form P = w/t fd/t joules/sec wattsP = w/t fd/t joules/sec wattsP = I V amp volts joules/sec kWP = I V amp volts joules/sec kWElectric Energy – how long energy is converted EE = Electric Energy – how long energy is converted EE = P t kWhP t kWhCost = kWh x cents/kWhCost = kWh x cents/kWhDirect Current – energy flows in one direction produced Direct Current – energy flows in one direction produced in batteriesin batteriesAlternating Current – current flows forth and back in Alternating Current – current flows forth and back in conductor 60 times every second 60Hz Adaptersconductor 60 times every second 60Hz AdaptersTransformers step up and step down voltageTransformers step up and step down voltage

Joke…………Joke…………

When is Electricity important to us?When is Electricity important to us?

Answer Answer

Always Always

What is so funny about that?What is so funny about that?

Nothing but…………….Nothing but…………….

I can’t even laugh without electricityI can’t even laugh without electricity