Transcript Modulation and simulation (MOD I1, Class A, S10) - IT

Modulation and Simulation
(MODI1-S10-TeamA)
Teacher: Poul Væggemose
Lesson 1 (week 7 – 2010)
MODI1-S10-TeamA
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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
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+
Battery
Current (Intro)
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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.
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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
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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
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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=?
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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=?
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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
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R = δ* L / π *r*r
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To illustrate the resistance in a wire, we will use a straw.
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A) Blowing into the straw to mark the air resistance (Reference resistance value).
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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).
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D) Press the straw on the midt section to reduce the radius ”r” and blow into the straw
(The reference resistance has become greater).
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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
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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.
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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.
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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.
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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.
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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
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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].
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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.
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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.
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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