* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Basic Electricity
Survey
Document related concepts
Nanogenerator wikipedia , lookup
Nanofluidic circuitry wikipedia , lookup
Giant magnetoresistance wikipedia , lookup
Cavity magnetron wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Power MOSFET wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Electric charge wikipedia , lookup
Opto-isolator wikipedia , lookup
Molecular scale electronics wikipedia , lookup
Galvanometer wikipedia , lookup
Current source wikipedia , lookup
Surge protector wikipedia , lookup
Current mirror wikipedia , lookup
Transcript
Basic Electricity Lesson 2 03/11/2007 by FJM Everything in the world, whether solid, liquid, or gas, is made up of atoms. • Each atom contains some number of electrons, protons, neutrons, and other sub-atomic stuff. • The nucleus (central region) of each atom contains the protons (positive charge) and neutrons (no charge). Electrons (negative charge) live in a cloud around the outside. • Since electrons and protons are charged particles, each atom prefers to have the same number of electrons as protons. 03/11/2007 by FJM 2 • Atoms of one or more types are organized into molecules. • There are only a hundred or so types of atoms, • There are an almost infinite number of different molecules. • Molecules are the building blocks from which all real objects are made.. • Molecules are not always so simple. • Some organic molecules can comprise hundreds of atoms 03/11/2007 by FJM 3 • For historical reasons, we divide the science and engineering of electrons into two parts; electricity, and electronics. – Electricity is the domain of motors, light bulbs, generators, and other "large scale" items. – Electronics has come to mean the domain of vacuum tubes, transistors, integrated circuits, and other "small scale" items. • . 03/11/2007 by FJM 4 • We have come to realize that orbits are not a very meaningful concept for electrons. • We now describe electrons as existing in a "cloud" that surrounds the atomic nucleus. • At any given instant, an electron has some statistical likelihood of being somewhere in that cloud.. 03/11/2007 by FJM 5 • Some materials are willing to let a few electrons move from molecule to molecule. • Materials that let electrons move through them are called "conductors". • Although some are better than others, most metals are good conductors of electricity. Silver, Gold, and Platinum are very good conductors but are expensive, so they are not often used. • Copper and Aluminum are reasonably good conductors and are fairly inexpensive. • Thus the wiring in our houses is copper, and the high voltage electric lines that we see crossing the country use aluminum cables.. 03/11/2007 by FJM 6 • Materials that do not let electrons move through them are called "insulators”. • Glass is an example of a type of material that keeps its electrons tightly controlled. • Glass is made of silicon molecules, organized very tightly in to crystalline structures. – Glass is an extremely good insulator. • Many plastics are good insulators too. – Plastics are cheap, flexible, and durable. – That is why the wiring in our houses is covered with a layer of plastic. 03/11/2007 • • • • by FJM 7 A single cell from a flashlight creates an electrical force of 1.5 Volts. A transistor radio battery creates an electrical force of 9 Volts. (There are six little cells of 1.5 Volts each inside of the 9 Volt battery.) Household electrical outlets are 110 or 120 Volts, What should you know about voltage? – Electrons don't move from atom to atom without a reason. – When electrons are flowing, there is an electrical force somewhere, pushing them along. – You might see references to Electromotive Force, or "EMF". 03/11/2007 by FJM 8 Current • Current is the flow rate of electrons through the circuit. . The water in your pipes is under pressure • This pressure is similar to Voltage. • Voltage is the pressure pushing on the electrons in a circuit. • If all of the faucets in your house are closed, no water flows through the pipes. • If you open one faucet, some water flows. If you open all of the faucets, a lot of water flows. • This flow of water is similar to electrical Current. 03/11/2007 by FJM 9 Voltage causes Current. • Voltage and current are not the same thing, although they are closely related. • In simple terms, Voltage causes Current. • Given a Voltage and a path for the electrons, current will flow. • Given the path, but no Voltage, or Voltage without the path, there will be no current. 03/11/2007 by FJM 10 Alessandro Volta • In 1791, Volta was experimenting with metals and acids and was able to assemble a pile of cells to form a battery • He touched a silver spoon and a piece of tin to his tongue (saliva is slightly acidic) and connected them with a piece of copper wire. • He experienced a "sour" taste, and realized he was experiencing an electrical phenomenon. • Each cell was a disk of zinc and a disk of silver, separated by a layer of brine-soaked pasteboard. • We now refer to that original battery as a Voltaic Pile. • In Volta's honor, we refer to electrical pressure as "Voltage" and 03/11/2007 by FJM 11 What Causes Voltage? • Electrons have a negative charge, and Protons have a positive charge. – Like-charged particles repel. – Opposite-charged particles attract. • • • • • Each charged particle that is out of balance exerts some electrical pressure as it tries to get back into balance. Electrons push, as they try to get away from each other. Protons pull, as they try to attract electrons towards them. The total amount of pressure between two points is measured as Voltage. Given a path, electrons will flow away from a negative charge and towards a positive charge 03/11/2007 by FJM 12 The Resistor • The resistor is a device that is common to practically every circuit known to man. • Resistors are designed to have specific values of resistance. Resistance opposes the flow of electrons. • A resistor is a device that limits the amount of current flowing through a circuit for a particular applied voltage. – If the resistance stays the same and the voltage goes down, then the current decreases. – If the voltage stays the same, and the resistance goes up, then the current decreases. – If the voltage stays the same, and the resistance goes down, then the current will increase. • The basic unit of resistance is the ohm. – 1 Ohm of resistance is defined as ... the resistance of a circuit in which a 1-amp current flows when 1 volt is applied. 03/11/2007 by FJM 13 The Resistor Code 03/11/2007 by FJM 14 The Capacitor • • • • • • Capacitance is the ability to store an electric field. The basic unit of capacitance is the Farad (abbreviated "F"). In a capacitor, there are two electric plates separated by an insulating material As the current flows, electrons build up on one plate. At the same time, electrons flow out of the other plate. Eventually, the capacitor is completely "charged up" and no more current will flow. With direct current, a capacitor would eventually become charged up and no more current would flow through the capacitor. With alternating current, and the current switched directions backwards, then the capacitor would start to "discharge" as the current began to flow the opposite direction. 03/11/2007 by FJM 15 Milli, Micro, Nano, Pico, 1 mili = 1/1,000th or .001 times the unit. (10-3) 1 micro = 1/1,000,000 or 0.000 001 times the unit (10-6 ) 1 nano = 1/1,000,000,000 or 0.000 000 001 times the unit (10-9 ) 1 pico = 1/1,000,000,000,000 or 0.000 000 000 001 times the unit (10-12 ) . 03/11/2007 by FJM 16 Digital Multipliers Table 1 Digit multipliers Multiplier (this times the first two digits !gives you the value in Pico-Farads) Third digit 0 1 1 10 2 100 3 1,000 4 10,000 5 100,000 6 not used 7 not used 8 .01 9 .1 A capacitor marked 104 is 10 with 4 more zeros or 100,000pF which is otherwise referred to as a .1 uF capacitor. 03/11/2007 by FJM 17 Electro-Magnet •We can create an electro-magnet by wrapping many turns of wire on a core, then causing an electrical current to flow through this coil of wire. •When the battery is not connected, there is no current flow, and therefore no magnetic field. •When the battery is connected, current flows through the coil, and a magnetic field is created, •The magnetic field curves around from one end of the coil to the other. –The field is strongest at the ends of the coil, and gets weaker as we get farther away. –We call the two ends of the coil the "poles"., one is "North" and the other is "South“ – When the battery is not connected, there is no current flow, and therefore no magnetic field. –When the battery is connected, current flows through the coil, and a magnetic field is created, as shown by the red lines. 03/11/2007 by FJM 18