165 lines
6.2 KiB
HTML
165 lines
6.2 KiB
HTML
<!DOCTYPE html PUBLIC "-//w3c//dtd html 4.0 transitional//en">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html;
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charset=windows-1252">
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<meta name="GENERATOR" content="Mozilla/4.7 [en] (X11; U; OSF1 V4.0
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alpha) [Netscape]">
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<meta name="Author" content="C. L. Davis">
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<title>Electricity - Static Electricity - Physics 299</title>
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</head>
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<body style="color: rgb(0, 0, 0); background-color: rgb(255, 255,
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255);" link="#0000ee" alink="#ff0000" vlink="#551a8b">
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<center>
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<h1> <img src="ULPhys1.gif" height="50" align="texttop"
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width="189"></h1>
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</center>
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<center>
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<h1>Electric Charge and Matter<br>
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</h1>
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</center>
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<center><img src="celticbar.gif" height="22" width="576"><br>
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<br>
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<font color="#ff0000"><i>"A new scientific truth does not triumph
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by
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convincing
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its opponents and making them see the light, but rather
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because its
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opponents
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eventually die, and a new generation grows up that is familiar
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with it"</i></font><br>
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Max Planck<br>
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</center>
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<img src="netbar.gif" height="40" align="middle" width="100%">
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<center><img src="anim_lightning.gif" height="100" align="middle"
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width="114"></center>
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<ul>
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<li> In order to feel an electric force an object must possess <b>ELECTRIC
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CHARGE</b>.</li>
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<br>
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<li> Electric charge can be either positive (+) or negative (-).</li>
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<br>
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<li> Electric charge is a fundamental property of matter
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(similar
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to mass). <br>
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The unit of electric charge is the <a
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href="http://www-gap.dcs.st-and.ac.uk/%7Ehistory/Mathematicians/Coulomb.html">Coulomb
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(C)</a> <img src="Coulomb.jpg" height="109" align="texttop"
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width="90"> <br>
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<br>
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One Coulomb is the amount of charge which flows through a wire
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carrying
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a current of 1 Ampere in one second. <br>
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<br>
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<img style="width: 31px; height: 30px;" alt="exclamation"
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src="exclamation-icon.gif"> Formally, as we will see later in
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this
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course, the unit of electric current - the Ampere - is the
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defined
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unit, one of the seven basic units (meters, kilograms, seconds,
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amperes, temperature, candela, mole). The Coulomb is then
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defined
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as Ampere.Seconds. However, in developing the basic theory
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of
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electricity it is more convenient to "pretend" that the Coulomb
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is the
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basic unit; the Ampere is then Coulomb/sec.</li>
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</ul>
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<div style="margin-left: 40px;"><img style="width: 31px; height:
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30px;" alt="exclamation" src="exclamation-icon.gif"> Electric
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charge is <span style="font-weight: bold; font-style: italic;">"quantized"</span>
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in
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units of the charge on the electron, e = 1.6 x 10<sup>-19</sup>
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C. That is charge always appears in integer multiples of
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"e". Unless we are dealing with individual atoms or
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sub-atomic
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particles, since the value of "e" is so small, this quantization
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is not
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apparent and need to be considered. </div>
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<ul>
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<li> <img src="tickred1.gif" height="48" width="48"> <b><u><font
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color="#ff0000"><font size="+2">Conservation of charge</font></font></u></b><img
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src="tickred1.gif" height="48" width="48"> </li>
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<br>
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<br>
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<br>
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<center>
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<p><img src="hot.gif" height="43" align="middle" width="79"> <b><i><font
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size="+2">"The net electric charge of an isolated system
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is
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constant"</font></i></b><img src="hot.gif" height="43"
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align="middle" width="79"> <br>
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<br>
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</p>
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</center>
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<p><b>However,<img src="exclamation-icon.gif" height="30"
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align="middle" width="31"> </b> Note that in calculating
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the net charge
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the <b><i>sign</i></b> of
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the charges must be taken into account, e.g. the net charge of a
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system
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containing objects with +2 C and -1 C is +1 C. </p>
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<p>The conservation of charge is a basic physical "law" in the
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same
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manner as mass, energy and momentum conservation. </p>
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<li> The force between two charges can be attractive or repulsive,
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depending on the relative signs of the charges. This fact
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can be
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expressed simply,</li>
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<br>
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<center>
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<p><b><i><font size="+1">"Like charges repel - unlike charges
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attract"</font></i></b></p>
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</center>
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<p><br>
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</p>
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<li> The magnitude of the force between charged objects is given
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by <a href="http://www.fact-index.com/c/co/coulomb_s_law.html">
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Coulomb
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's</a> Law (see later section for detailed description).</li>
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</ul>
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<ul>
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<li>Most useful/interesting electrical phenomena occur as electric
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charge is transferred from one place to another. Where
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possible
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electric charge will "flow" to minimize the total energy
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of a
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system. However, initially, we will discuss static
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situations,
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where the charges are held in place by some external mechanism.<br>
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</li>
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</ul>
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<p><br>
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<img src="netbar.gif" height="40" width="100%"> </p>
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<center>
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<p style="color: rgb(255, 0, 0); font-style: italic;"
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class="MsoNormal">"If
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I
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were
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as
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rich
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as
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Rockerfeller, I'd be richer than
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Rockerfeller" <br>
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"How's that?" <br>
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"I'd do a bit of window cleaning on the side"</p>
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Ronnie Barker<br>
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<br>
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<img src="celticbar.gif" height="22" width="576"> <br>
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<p><i>Dr. C. L. Davis</i> <br>
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<i>Physics Department</i> <br>
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<i>University of Louisville</i> <br>
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<i>email</i>: <a href="mailto:c.l.davis@louisville.edu">c.l.davis@louisville.edu</a>
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<br>
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</p>
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<p><img src="header-index.gif" height="51" width="92">
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</p>
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</center>
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<p><br>
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</p>
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</body>
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</html>
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