Defining Electricity Defining Electricity and its Major and its Major ComponentsComponents

Mr. ScheuMr. Scheu

So what is this mysterious stuff So what is this mysterious stuff that we call electricity?that we call electricity?

Electricity surrounds us and for most of us, life without Electricity surrounds us and for most of us, life without electricity would be totally different. Electricity can be used electricity would be totally different. Electricity can be used in a wide variety of waysin a wide variety of ways– For example: For example:

Electric motors turn electricity into motion. (locomotives)Electric motors turn electricity into motion. (locomotives) Light bulbs turn electricity into light Light bulbs turn electricity into light Computers turn electricity into information. (this PowerPoint)Computers turn electricity into information. (this PowerPoint) TVs turn electricity into moving pictures. (the Young Frankenstein TVs turn electricity into moving pictures. (the Young Frankenstein

DVD)DVD) Speakers turn electricity into sound waves. (music on your radio)Speakers turn electricity into sound waves. (music on your radio) Toasters, hair dryers and space heaters turn electricity into heat. Toasters, hair dryers and space heaters turn electricity into heat. X-ray machines turn electricity into X-rays. X-ray machines turn electricity into X-rays.

How would life be without electricity?How would life be without electricity?– we would revert back to fireplaces for heat, wood-fired stoves we would revert back to fireplaces for heat, wood-fired stoves

for cooking, candles for light and the slide rules for for cooking, candles for light and the slide rules for computation, and to talk over long distances, we are left with computation, and to talk over long distances, we are left with smoke signals and postcards. smoke signals and postcards.

ObjectivesObjectives

Today we will:Today we will:– Define electrical terms Define electrical terms – Discuss the components of an electrical Discuss the components of an electrical

circuitcircuit– Describe how electrical energy is Describe how electrical energy is

measured measured – Define Ohm’s law and illustrate the Define Ohm’s law and illustrate the

relationship between voltage, amperage, relationship between voltage, amperage, watts, and ohms of resistancewatts, and ohms of resistance

Electricity BasicsElectricity Basics

Electricity—Electricity—– a a sourcesource of of energyenergy

that can be that can be converted to converted to lightlight, , heat, or power.heat, or power.

– A movement of A movement of electrons known as electrons known as electrical currentelectrical current

Theories of Current FlowTheories of Current Flow

Electron Theory of Electron Theory of Current FlowCurrent Flow– Belief that electrons Belief that electrons

flow from a flow from a negativelynegatively charged charged atom to a atom to a positivelypositively charged electronscharged electrons

Conventional Conventional Theory of Current Theory of Current FlowFlow– Theory that current Theory that current

flowed from flowed from positivelypositively charged charged atoms to atoms to negativelynegatively charged atomscharged atoms

Both Theories are still in use today, and it is important to not confuse the two.

Electrical CircuitsElectrical Circuits A simple circuit must A simple circuit must

containcontain1)1) A A sourcesource of electricity to of electricity to

start the flow of electrons start the flow of electrons (a battery, etc.)(a battery, etc.)

2)2) A conductor that the A conductor that the electrons flow throughelectrons flow through

3)3) a a load load or or consumerconsumer to use to use the flow of electrons (a light the flow of electrons (a light bulb, motor, etc.)bulb, motor, etc.)– LoadLoad—any device that —any device that

converts electrical energy converts electrical energy into another form of into another form of useable energyuseable energy

4)4) A conductor connected A conductor connected from the load, back to the from the load, back to the sourcesource

Complete vs incomplete circuitComplete vs incomplete circuit

source

load

Wires

Generating Electrical Generating Electrical CurrentCurrent

Where is electricity generated?Where is electricity generated?– Electricity is produced from a generator Electricity is produced from a generator

(example: power plant)(example: power plant)– GeneratorGenerator—converts energy from other —converts energy from other

forms, and causes forms, and causes electronselectrons to flow to flow through the circuitthrough the circuit Examples of converted energy include:Examples of converted energy include:

– WaterWater– SteamSteam– WindWind– Any others?Any others?

Other types of generators…Other types of generators…

Storage BatteriesStorage Batteries (chemical (chemical generators): generate electrical generators): generate electrical current by chemical reactions from current by chemical reactions from chemicals chemicals storedstored inside the batteries inside the batteries– Wet-cell batteryWet-cell battery– reaction between the – reaction between the

electrodes and the electrolyte solutionelectrodes and the electrolyte solution– Dry-cell batteryDry-cell battery—electrolyte is a —electrolyte is a

compound in a paste formcompound in a paste form

Other types of generators…Other types of generators…

Mechanical energy: Mechanical energy: a a magnetic forcemagnetic force is is used to move electrons; known as used to move electrons; known as electromagnetic inductionelectromagnetic induction

Piezo electricity: Piezo electricity: electricity that is electricity that is produced when produced when pressurepressure or or forceforce is is appliedapplied

Thermoelectric process: Thermoelectric process: electricity electricity produced by produced by heat energyheat energy; the more heat, ; the more heat, the more current producedthe more current produced

Solar power: Solar power: uses uses photocellsphotocells to generate to generate electrical currentelectrical current

Journey of ElectricityJourney of Electricityfrom being generated to usefrom being generated to use

Conductors and InsulatorsConductors and Insulators

ResistanceResistance—tendency of an element or —tendency of an element or material to prevent electrical flowmaterial to prevent electrical flow

ConductorsConductors—elements and materials that —elements and materials that have have lowlow resistance (Gold, Silver, and resistance (Gold, Silver, and Copper are good conductors)Copper are good conductors)

InsulatorsInsulators—elements that do —elements that do notnot readily readily allow electrical current to flow through allow electrical current to flow through them (glass, porcelain, cotton, dry wood)them (glass, porcelain, cotton, dry wood)– Insulating ability may be lost when material Insulating ability may be lost when material

becomes wetbecomes wet

How Electrical Energy is How Electrical Energy is MeasuredMeasured

Electrical current—the flow of Electrical current—the flow of electrons through the conductor; electrons through the conductor; measured in measured in amperesamperes ( (AA or or ampsamps for short)for short)

AmperageAmperage——the rate of the rate of electrical electrical currentcurrent flow per flow per secondsecond

Similar to flow of water (gallons per Similar to flow of water (gallons per minute) of water pumpminute) of water pump

How Electrical Energy is How Electrical Energy is MeasuredMeasured

VoltageVoltage ((V V or or volt)–volt)– potential potential forceforce that causes current to flow in that causes current to flow in conductorconductor

Compared to Compared to pounds per square inch pounds per square inch of pressureof pressure in the water pipe in the water pipe

Current Current cannotcannot exist without the exist without the pressure of pressure of voltagevoltage to force it to force it through the conductorthrough the conductor

How Electrical Energy is How Electrical Energy is MeasuredMeasured

Electrons do not flow freely through even the best Electrons do not flow freely through even the best conductors, just as water must overcome friction conductors, just as water must overcome friction of the pipe wall to flow through a pipeof the pipe wall to flow through a pipe

OhmOhm ( ( ΩΩ )– )– the unit of measure of the resistance the unit of measure of the resistance to to electrical flowelectrical flow– Affected byAffected by

The elements of which the conductors are madeThe elements of which the conductors are made Length of conductorsLength of conductors

– The The longelonger the conductor, the r the conductor, the greatergreater the resistance to current the resistance to current flowflow

Cross-sectional area of conductorsCross-sectional area of conductors– TheThe smaller smaller the diameter of the wire, the the diameter of the wire, the greatergreater the the

resistance to flowresistance to flow Temperature of conductorTemperature of conductor

– The The hotterhotter the wire, the the wire, the moremore resistance to current flow resistance to current flow

Relating Voltage, Amperage, Relating Voltage, Amperage, and Ohms of Resistanceand Ohms of Resistance

Ohm’s law--the flow of electricity through the conductor is always Ohm’s law--the flow of electricity through the conductor is always directly proportional to the voltage it producesdirectly proportional to the voltage it produces

Volts

Amperage X Ohms

Amperes= Volts/Ohms Volts= Amperes x Ohms

Ohms= Volts/Amperes

Ohm’s Law in Triangle expression

Example ProblemsExample Problems20 A = 120 V

6 Ohms 120 V = 20 A x 6 Ohms

6 Ohms = 120 V

20 A

Relating Voltage, Amperage, Relating Voltage, Amperage, and Wattsand Watts

Watt—a measure of electrical power, or the amount of electrical energy Watt—a measure of electrical power, or the amount of electrical energy the load or consumer usesthe load or consumer uses

The higher the wattage the rating, the faster the electrical energy is being The higher the wattage the rating, the faster the electrical energy is being convertedconverted

Watts

Amperage X Voltage

Volts= Watts/Amps Watts= Volts x Amps

Amps= Watts/Volts

Wattage formulas in Triangle Expression

Sample Problem:Sample Problem:

Suppose six large 200-watt bulbs are Suppose six large 200-watt bulbs are to be installed in a 120 volt electrical to be installed in a 120 volt electrical circuit. How many amps must flow circuit. How many amps must flow when the lights burn at rated when the lights burn at rated wattage? The source of electrical wattage? The source of electrical current will supply 120 volts of current will supply 120 volts of pressure. Six bulbs will draw 1,200 pressure. Six bulbs will draw 1,200 watts of power or energy (6 x 200 = watts of power or energy (6 x 200 = 1,200 watts).1,200 watts).

SolutionSolution

Which formula must we use?Which formula must we use? A=W/VA=W/V (1200 watts/120 volts) = 10 amps(1200 watts/120 volts) = 10 amps

ActivityActivity

Complete the worksheet using the Complete the worksheet using the given formulas for calculating amps, given formulas for calculating amps, volts, ohms and wattsvolts, ohms and watts

ReviewReview What is electricity?What is electricity? What are the 3 components of an What are the 3 components of an

electrical circuit?electrical circuit? Describe how electrical energy is Describe how electrical energy is

measured, and what the different terms, measured, and what the different terms, such as amps, volts, and ohms mean.such as amps, volts, and ohms mean.

Tomorrow, we will continue our discussion Tomorrow, we will continue our discussion on electricity as we begin to talk about on electricity as we begin to talk about wiring outlets and light fixtures and other wiring outlets and light fixtures and other appliances within our homes.appliances within our homes.