ELECTRICAL PRINCIPLES Electricity is the major power source of stationary equipment Uses: Driving Machinery Lighting Heating Cooling Knowledge of electricity is essential for safe use of electrical equipment

Electricity- a form of energy that can produce Electricity- a form of energy that can produce light, heat magnetism and chemical changes Light- produced by heating a special metal element or filament in a vacuum tube called a “bulb”. Electricity flows through certain gases causing them to glow Insulator- provides great resistance to the flow of electricity Materials: rubber-glass-vinyl-air

Amperes- measure of the rate of flow of electricity in a conductor Volts- measure of electrical pressure Watts- measure of the amount of energy that can be completed by amps and volts Formulas: Watts=volts x amps Volts=watts x amps Amps=watts x volts W V A

Fluorescent lamp- glows as a result of electricity Fluorescent lamp- glows as a result of electricity flowing through a gas Heat- is produced when electricity flows through metals with some difficulty Resistance- tendency of a material to prevent electricity to flow Conductor- metal permits electricity to flow easily Materials: silver-aluminum-copper

E = I X R used in outdoors used in wiring for homes heat develops in implements Ohm’s Law: used to measure a material’s resistance to the flow of electrical current E=volts I=amps R=resistance E = I X R

Magnetism- force that attracts or repels iron or steel - permanent magnet - when iron or steel holds its magnetism 2 ends or poles - north - south Opposites attract/likes repel

Magnetic field- force between 2 objects Electric Motors- principle of magnetism is the basis upon which electric motors operate Reverses the Polarity: reversing the direction of current flow Electromagnet- unit is called Commutator- reveres the current flow in an electric motor Armature- rotating magnet

magnetic forces around the armature are called the “field” Generators & Alternators- produce electricity Generator- produces current (direct) - flows one way Alternator- produces current (alternating) Turbine- high speed rotary engine driven by water-steam-gas Circuits- circle of electricity - open circuit- broken - closed circuit- together

Short Circuit- flow through the circle & back Short Circuit- flow through the circle & back to the source too rapidly Grounding- connection between a piece of equipment & the earth - ground rod- steel or copper - ground wire- bare * channels stray electricity Electricity Safety: 2 deadly hazards with current - shock - fire

Shock- body’s reaction to a current GFCI- Ground Fault Circuit Interrupter -cuts off electricity if it leaves the pathway Electrical Wiring: Systems have to be: -safe -convenient -neat -expandable -provide sufficient current Service Entrance: Power company provides -transformer -service drop -appropriate wiring

Entrance Head- waterproof device used to. attach exterior wires to Entrance Head- waterproof device used to attach exterior wires to interior wires Transformer- converts high voltage to 240 volts-usable form for homes - step up - step down Service Drop- assembly of electrical wires- connectors & fasteners used to transmit electricity from the transformer to the entrance head

Service Entrance Panel- box with fuses or. breakers where Service Entrance Panel- box with fuses or breakers where electricity enters a building Meter- measurement of electricity in kilowatt hours-Kilo means 1, 000 Watt Hour- use of 1 watt for 1 hour Kilowatt Hour- use of 1, 000 watts for 1 hour Reading a Meter: the last number passed by each pointer is read

1st & 3rd dials turn counterclockwise 2nd & 4th dials turn clockwise Branch Circuits- branch out to a variety of places for many purposes Fuse: plug or cartridge containing a strip of metal that melts when more than a specified amount of current passes through Circuit Breaker:

switch that trips & breaks the circuit when more than specified amounts pass through it - reset breaker after it trips Types of Cables: 3 systems of wiring: -Non-metallic sheathed -Armored cable -Conduit

Non-metallic Sheathed Cable: -copper/aluminum -waterproof -approved for burial Armored Cable: -flexible metal sheath -mechanical damage protection Conduit: Tubing consists of individual insulated wires EMT-electrical metallic tube

Conduit can be: -rigid -bendable -provide the most protection Wire Type & Size: Copper Aluminum Wire size designated by gauge: lower the gauge larger the wire

Strands- small wires placed together are called “bundles” - improves conductivity & flexibility - electricity carried on outside of wire Voltage Drop- refers to a loss of voltage as the electricity travels along a wire -larger the wire, less voltage drop -longer the wire, more voltage drop Wire ID: factors to determine wire -outer covering -number of wires

-individual wire covering -cable construction Wire type is stamped on outside Type T- dry locations Type TW- dry or wet locations Type THHN- dry locations, high temperatures Type THW & THWN- wet locations, high temperatures Type XHAW- high moisture & heat resistance

Type UF- buried in soil (not concrete) NEC- National Electric Code Hot Wires- colors (positive) -black -red -blue Neutral Wires- color -white Ground Wire- colors -green -bare Typical markings: 12-1, 12-2, 12-3 with ground

INSTALLING BRANCH CIRCUITS NEC- controls restrictions on wiring Wiring Boxes: -metal -plastic -hold work in place -nail or screw to framing -contains all electrical connections -square/octagonal/rectangular

Wire Nuts- insulated, solder-less connectors Receptacle- device used for receiving electrical plugs Switch- device used to stop the flow of electricity Duplex Receptacle- both outlets are on same circuit Single-Pole Switch- designed to be the only switch in the circuit Knock Out- partially punched impression

Ground Clip- attaches ground wire to a box Testing a Circuit: Continuity Tester- device used to determine if electricity can flow between 2 points Continuity- connected-ness 3 way switch- permits a light/receptacle to be controlled from 2 locations