Notes taken from Gillette’s Designing with Light

Atoms are the smallest complete building block in nature Atoms are made up

of:Protons - positive

chargeElectrons - negative

chargeNeutrons - neutral

charge

A stable atom # of electrons in

orbit around the nucleus = # of protons in the nucleus

Ie. Hyrdrogen

Electron

Nucleus

Law of Charges Like charges repel and unlike charges attract

Two protons would defy attempts to be close togetherSame with electrons

An electron and proton would stick together

Valence shell: the outermost plane of orbiting electrons in the structure of an atom Weak force holds electron in orbit

Free electrons: an electron that has broken away from its “home” atom to float free Copper

Electrical current The flow or movement of electrons through a

conductor

Ampere: the unit of measurement of electrical current

Potential: the difference in electrical charge between two bodies; measured in volts

Volt: the unit of measurement of electrical potential

There are two types of electrical current: Direct current (DC)

The flow of electrons in one direction. AKA: Batteries

Short distances

There are two types of electrical current: Alternating current (AC)

Transmitted over long distances The flow of electrons is reversed on a periodic

basis. Utility companies

http://www.answers.com/topic/alternating-current

3 parts Source: the origin of electrical potential

battery or 120-volt wall outlet Load: a device that converts electrical energy

into another form of energy Lamp or motor

Circuit: a conductive path through which electricity flows Wire or cable

Series In a series circuit all of the electricity flows

through every element of the circuit

If any of the loads don’t work then the circuit will be broken, the electricity won’t flow, and the remaining loads won’t work either

Series

www.berkeleypoint.com/images/series.jpg

Parallel In a parallel circuit only a portion of the

electricity flows through each of the branches of the circuit

If one load on a circuit doesn’t work then the electricity will continue to flow in the rest of the circuit and the other loads will continue to work

Parallel

www.berkeleypoint.com/images/series.jpg

The Combination Circuit Combines the principles of the two primary

circuits. Any electrical circuit that uses a switch to

control a load is an example of a combination circuit.

Ohm’s Law As voltage increases, current increases; as

resistance increases, current decreases Resistance

Opposition to electron flow within a conductor Depends on chemical makeup Measured in Ohm’s

Low-voltage systems

Ohm’s Law I=current in amperes E=voltage in volts R=resistance in ohms

I=E/R E=IR R=E/I

Power Formula Higher voltage Watts

Unit of measurement of power required to do work

Amount of electrical energy converted or consumed

Converted into light, heat or mechanical energy

Power Formula “PIE” P=power in watts I=current in amperes E=voltage in volts

Power Formula “PIE”

P=power in watts I=current in

amperes E=voltage in volts

P=IE

West Virginia W=power in watts V=voltage in volts A=current in

amperes

W=VA

Dimmer Voltage = 120VAC Dimmer can handle 20 amperes of

current What is the maximum safe load that can

be placed on this dimmer

How many 575W instruments can you plug into a 2400W dimmer with cable that can carry 20 amperes of current?

How many 750W instruments can you plug into a 2400W dimmer with cable that can carry 20 amperes of current?

System Voltage = 120VAC 14 gauge cable connecting the

instruments can carry 15 amperes How many 500 watt instruments can be

loaded onto a dimmer?

Conductor Any material with an abundance of free

electrons Water, copper, silver, gold, aluminum

Insulator Any material with few free electrons Air, glass, paper, rubber, most plastics

Created when a large SURGE of current causes a portion of the conductor to explosively melt

Provides a low resistance path for the electricity to follow in case of a short circuit between the hot wire and the devices metallic housing

http://sol.sci.uop.edu/~jfalward/physics17/chapter8/plugwithground.jpg

Electrical cable containing hot, neutral and ground wires

Connects lighting instrument to the power source

Plug Male portion of a connecting device

Receptacle Female portion of a connecting device

Many hand tools do not have ground pins Instead they have an outer plastic

insulation that protects you from a short circuit

The grounding point Usually a metal rod driven into the

ground or an underground metal water pipe

http://en.wikipedia.org/wiki/Image:HomeEarthRodAustralia1.jpg

HOT = BLACK, occasionally RED GROUND = GREEN NEUTRAL = WHITE

Greater current in system than it was designed to handle

Fuse and circuit breaker protects from overload Must have matching amperage as system

Fuse Contains a soft metallic strip that melts when

the current exceeds what the system is designed for

Must be replaced when “blown”

http://www.m-99.co.uk/Car_Audio/Car_Fuses/gold_fuse.jpg images/jpegs/fuse30a.jpgimages.orgill.com/200x200/4180923.jpg

Circuit Breaker Like a switch Bimetal strip flexes to trip circuit if overloaded

cache.smarthome.com/images/7103.jpg

1. If you don’t know what you are doing, don’t do it. Ask for help.

2. Use tools covered with plastic or rubber insulation

3. Use wooden or fiberglass ladders

4. Disconnect device from circuit before you work on it.

5. Use common senseDon’t touch bare wiresDon’t work in damp locations or put drink where it could spill

Don’t intentionally overload circuit

Don’t try to bypass fuse or circuit breaker

6. Maintain ground circuits

7. Check cables and connectors periodically. Replace cracked, chipped or deteriorating equipment

8. Keep cables and connectors clean.

9. Store cables neatly with ends plugged together and tied

10. Disconnect plug by pulling on body of plug.

11. Ensure all elements have same electrical rating.