* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Chapter 3: Electrical Theory and Practice
Integrated circuit wikipedia , lookup
Regenerative circuit wikipedia , lookup
Electrical connector wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Power electronics wikipedia , lookup
Nanogenerator wikipedia , lookup
Power MOSFET wikipedia , lookup
Nanofluidic circuitry wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Opto-isolator wikipedia , lookup
Index of electronics articles wikipedia , lookup
Electromigration wikipedia , lookup
RLC circuit wikipedia , lookup
Current mirror wikipedia , lookup
Surge protector wikipedia , lookup
Notes taken from Gillette’s Designing with Light Atoms are the smallest complete building block in nature Atoms are made up of: Protons - positive charge Electrons - negative charge Neutrons - 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 together Same 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.m99.co.uk/Car_Audio/Car_Fuses/gold _fuse.jpg images.orgill.com/200x200/4180923.jpg images/jpegs/fuse30a.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 sense Don’t touch bare wires Don’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.