Electrical Principles and Electrical Principles and Wiring MaterialsWiring Materials

Original Power Point Created by Casey Osksa

Modified by Georgia Agricultural Education Curriculum Office

June 2002

Principles of ElectricityPrinciples of Electricity

Electricity is a form of energy that can Electricity is a form of energy that can produce light, heat, magnetism, chemical produce light, heat, magnetism, chemical changeschanges

Resistance: tendency of a material to Resistance: tendency of a material to prevent electrical flowprevent electrical flow

Conductor: if electricity flows easilyConductor: if electricity flows easily Insulator: material that provides great Insulator: material that provides great

resistanceresistance

Amps, Volts, WattsAmps, Volts, Watts

Amperes: measure of the rate of flow of Amperes: measure of the rate of flow of electricity in a conductorelectricity in a conductor

Volts: measure of electrical pressureVolts: measure of electrical pressure Watts: measure of the amount of energy Watts: measure of the amount of energy

or work that can be doneor work that can be done Ohms: measure of electrical resistance Ohms: measure of electrical resistance

to flowto flow

Ohm’s LawOhm’s Law

Ohm = ROhm = R Volts = EVolts = E Amps = IAmps = I Ohm’s Law: E = IROhm’s Law: E = IR

I=E/R I=E/R

R=E/IR=E/I

Electrical SafetyElectrical Safety Shock and FireShock and Fire Never disconnect any safety deviceNever disconnect any safety device Don’t touch electrical items with wet hands Don’t touch electrical items with wet hands

or feetor feet Don’t remove ground plug prongDon’t remove ground plug prong Discontinue use of extension cord that feels Discontinue use of extension cord that feels

warmwarm Don’t put extension cords under carpetDon’t put extension cords under carpet

Electrical SafetyElectrical Safety Install wiring according to code regulationsInstall wiring according to code regulations Blown fuse or breaker, determine causeBlown fuse or breaker, determine cause Don’t replace fuse with larger fuseDon’t replace fuse with larger fuse Don’t leave heat producing appliances Don’t leave heat producing appliances

unattendedunattended Heaters & lamps away from combustiblesHeaters & lamps away from combustibles Don’t remove back of TV (30,000v when off)Don’t remove back of TV (30,000v when off) Electric motors lubricated, free of grease etc.Electric motors lubricated, free of grease etc.

Electrical SafetyElectrical Safety

Keep appliances dryKeep appliances dry Don’t use damaged switches, outlets, Don’t use damaged switches, outlets,

fixtures, extension cordsfixtures, extension cords Follow manufacturer’s instructions for Follow manufacturer’s instructions for

installation and use of electrical installation and use of electrical equipmentequipment

Service EntranceService Entrance Power from from power companyPower from from power company Transformer: drops volts from 25,000 volts Transformer: drops volts from 25,000 volts

to 240 voltsto 240 volts Service drop: wires etc from transformer to Service drop: wires etc from transformer to

househouse Entrance head: weather-proof at houseEntrance head: weather-proof at house Meter: $$$Meter: $$$ Service Entrance Panel (SEP): box with Service Entrance Panel (SEP): box with

fuses or breakersfuses or breakers

Electric MeterElectric Meter

Kilowatthours: how electricity is soldKilowatthours: how electricity is sold Kilo = 1000Kilo = 1000 Watthour = use of 1 watt for one hourWatthour = use of 1 watt for one hour

100 watt light bulb for 1 hour - 100 100 watt light bulb for 1 hour - 100 watthourswatthours

Kilowatthour = 1000 watts for one hourKilowatthour = 1000 watts for one hour

Branch CircuitsBranch Circuits

usually begin at SEPusually begin at SEP branch out into a variety of placesbranch out into a variety of places only 1 motor or;only 1 motor or; series of outlets or;series of outlets or; series of lightsseries of lights use correct size wire and fuse or use correct size wire and fuse or

breakerbreaker

Types of CableTypes of Cable

Nonmetallic sheathed cable: copper or Nonmetallic sheathed cable: copper or alluminum wire covered with paper, alluminum wire covered with paper, rubber, or vinyl for insulationrubber, or vinyl for insulation

Armored cable: flexible metal sheath Armored cable: flexible metal sheath with individual wires inside. Wires are with individual wires inside. Wires are insulatedinsulated

Conduit: tubing with individually Conduit: tubing with individually insulated wiresinsulated wires

Wire Type and SizeWire Type and Size coppercopper No 14 (14 gauge) = 15 amp circuitsNo 14 (14 gauge) = 15 amp circuits No 12 = 20 ampsNo 12 = 20 amps No 10 = 30 ampsNo 10 = 30 amps aluminum use one size largeraluminum use one size larger lower gauge number = larger wirelower gauge number = larger wire No 8 and larger use bundles of wiresNo 8 and larger use bundles of wires current travels on outer surface of wire, so a current travels on outer surface of wire, so a

bundle of smaller wires can carry morebundle of smaller wires can carry more

Voltage DropVoltage Drop

loss of voltage as it travels along a wireloss of voltage as it travels along a wire lights dim, motors overheatlights dim, motors overheat larger wires have less voltage drop for a larger wires have less voltage drop for a

given amount of currentgiven amount of current longer wire = greater problemlonger wire = greater problem must increase wire size as distance must increase wire size as distance

increasesincreases

Wire IdentificationWire Identification

Color coded: black, red, & blue = Color coded: black, red, & blue = positive or hot wires which carry current positive or hot wires which carry current to appliancesto appliances

White = neutral wires carry current from White = neutral wires carry current from appliance back to sourceappliance back to source

Green or Bare = ground all metal boxes Green or Bare = ground all metal boxes and appliancesand appliances