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Modulation and Simulation (MODI1-S10-TeamA) Teacher: Poul Væggemose Lesson 1 (week 7 – 2010) MODI1-S10-TeamA 2013327 2027885 2027888 2037352 2037356 2037357 2037360 2037361 2037371 2037373 2037375 2037380 2037381 2037384 2037385 2037388 2037393 2037421 2037606 2037934 2038210 56533 2007937 2007934 Daisy Mukasi Idehen Jonas Fabricius Pape Paw Ormstrup Madsen Peter Dimitrov Mihaela Lyubomirova Mitsova Petko Velichkov Tsutsumanov Wilmer Entena Diana Krasteva Georgieva Adrian Plamenov Bezev Rimon Joni Istifan Nassori Ilian Rumenov Slavchev Andrius Baliutavicius Vytautas Andrijauskas Marius Jurksaitis Ammar Abdul Kareem Jamah Toms Viksna Ernestas Kvederas Neville Anderson Osvaldas Rokas Kajantha Elango Linas Jasiulis Ushanthan Jeganathan George Parselyan Diana Dumitrascu Electrons (Intro) • The electron is a subatomic particle that carries a negative electric charge. It has no known components or substructure, and therefore is believed to be an elementary particle (Joseph John Thomson, year 1897). • Electrons (e-) are moving from minus (-) to plus (+). e- eResistor - + Battery Current (Intro) • Electric current means, depending on the context, a flow of electric charge (a phenomenon) or the rate of flow of electric charge (a quantity). This flowing electric charge is typically carried by moving electrons, in a conductor such as wire; in an electrolyte, it is instead carried by ions, and, in a plasma, by both. The SI unit for measuring the rate of flow of electric charge is the ampere. Electric current is measured using an ammeter. • The ampere is a measure of the amount of electric charge passing a point per unit time. Around 6.242 × 1018 electrons passing a given point each second constitutes one ampere. (Since electrons have negative charge, they flow in the opposite direction to the conventional current.) • Current (I) are moving from plus (+) to minus (-). I I Resistor - + Battery Resistance in a wire • • • • • • • Area of wire = A = π*r*r Radius of wire = r Resistivity (δ) = R*A / L R*A = δ *L R = δ*L/ A A = π *r*r R = δ* L / π *r*r Example 1-2-3 • • • • • • Example 1 (Stainless Steel type 304 wire) Pi: π = 3,14 Radius: r = 0,005 cm Resistivity: δ = 72 μ ohm-cm Length: L = 3,82 cm R=? • • • • • • Example 2 (thicker wire) Pi: π = 3,14 Radius: r = 0,006 cm Resistivity: δ = 72 μ ohm-cm Length: L = 3,82 cm R=? • • • • • • Example 3 (thinner wire) Pi: π = 3,14 Radius: r = 0,004 cm Resistivity: δ = 72 micro ohm-cm Length L = 3,82 cm R=? Straws attempt • R = δ* L / π *r*r • To illustrate the resistance in a wire, we will use a straw. • A) Blowing into the straw to mark the air resistance (Reference resistance value). • B) Clip the straw into 2 equal parts to reduce the length. Blow into one of the straws and you will feel less wind resistance (The reference resistance has been reduced). • D) Press the straw on the midt section to reduce the radius ”r” and blow into the straw (The reference resistance has become greater). • E) What will happen to the wind resistance if you blow through both your straws (parallel) instead of just one straw with equal length ? Will the wind resistance be equal, less or greater? AC – Alternating Current • In alternating current (AC, also ac) the movement (or flow) of electric charge periodically reverses direction. An electric charge would for instance move forward, then backward, then forward, then backward, over and over again. In direct current (DC), the movement (or flow) of electric charge is only in one direction. • Used generically, AC refers to the form in which electricity is delivered to businesses and residences. The usual waveform of an AC power circuit is a sine wave, however in certain applications, different waveforms are used, such as triangular or square waves. Audio and radio signals carried on electrical wires are also examples of alternating current. In these applications, an important goal is often the recovery of information encoded (or modulated) onto the AC signal. • The big advantage that alternating current provides for the power grid is the fact that it is relatively easy to change the voltage of the power, using a device called a transformer. Power companies save a great deal of money this way, using very high voltages to transmit power over long distances. • How does this work? Well, let's say that you have a power plant that can produce 1 million watts of power. One way to transmit that power would be to send 1 million amps at 1 volt. Another way to transmit it would be to send 1 amp at 1 million volts. Sending 1 amp requires only a thin wire, and not much of the power is lost to heat during transmission. Sending 1 million amps would require a huge wire. • The power that comes from a power plant, on the other hand, is called alternating current (AC). The direction of the current reverses, or alternates, 60 times per second (in the U.S.) or 50 times per second (in Europe, for example). The power that is available at a wall socket in the United States is 120-volt, 60-cycle AC power. I EU it is 240-volt, 50-cycle (Hertz) AC power. The Alternating Current Generator. • http://www.ul.ie/~gaughran/flynn/real.gif • Basically the generator is the opposite of the motor. • In this case the rotation of the coil produces a current. • The current produced is an alternating one. • The split rings are replaced with two slip rings. DC – Direct Current • Batteries, fuel cells and solar cells all produce something called direct current (DC). The positive and negative terminals of a battery are always, respectively, positive and negative. • Current always flows in the same direction between those two terminals. AC / DC History • A bitter rivalry between electricity-savvy inventors may sound fictional, but the tension between Thomas Edison and Nikola Tesla was real. Tesla championed alternating current, while Edison insisted that it was too dangerous. The only casualties in this "war of currents" were the animals Edison publicly electrocuted with Tesla's high voltage system to prove his point. The early victims were dogs and cats, but Edison eventually electrocuted an elephant named Topsy [source: Ruddick]. • So power companies convert alternating current to very high voltages for transmission (such as 1 million volts), then drop it back down to lower voltages for distribution (such as 1,000 volts), and finally down to 120 volts inside the house for safety. As you might imagine, it's a lot harder to kill someone with 120 volts than with 1 million volts (and most electrical deaths are prevented altogether today using GFCI outlets). To learn more, read How Power Grids Work. • But this special feature isn't about the two electrical systems and how they worked. Rather, it's a simple explanation that shows the difference between AC and DC. • http://images.google.dk/imgres?imgurl=http://www.pbs.org/wgbh/amex/edison/sfeature/images/acdc_al l_off.gif&imgrefurl=http://www.pbs.org/wgbh/amex/edison/sfeature/acdc.html&usg=__dBAFutZlcN6s9oI SKVRnK3xdjg8=&h=279&w=235&sz=9&hl=da&start=1&um=1&itbs=1&tbnid=umCbbzZzimCcHM:&tbnh=1 14&tbnw=96&prev=/images%3Fq%3Dalternating%2Bcurrent%26hl%3Dda%26sa%3DX%26um%3D1 Electrons (Links 1) Protons, neutrons and electrons http://www.youtube.com/watch?v=-P4N-0Wbtyk Electronic circuit analysis vol 1 http://www.authorstream.com/Presentation/livycat-226325-electric-circuitanalysis-vol-1-education-ppt-powerpoint/ Structure of electron: An important scientific discovery! http://www.youtube.com/watch?v=1Wn06fXlYn4 The Silicon Web: Physics for the Internet Age http://thesiliconweb.net/SiliconWeb_Contents_files/Sec%205.6.pdf Electrons (Links 2) • Current and Voltage • http://www.youtube.com/watch?v=1xPjES-sHwg • Electric current • http://www.youtube.com/watch?v=5laTkjINHrg&feature=related • Intro to ohms law • http://www.youtube.com/watch?v=_-jX3dezzMg&NR=1&feature=fvwp • Ohm's Law Part 1: Units and Quantities • http://www.youtube.com/watch?v=JRp_iSaVRjE&feature=related • Ohm's Law Part 2: Ohm's Law Applied to Simple Circuits • http://www.youtube.com/watch?v=FwEz9ygPHiM&feature=related