117 lines
4.4 KiB
HTML
117 lines
4.4 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 - Electric Dipole - 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 Field due to a Dipole<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>"</i></font><font color="#ff0000"><i>
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<meta http-equiv="content-type" content="text/html;
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charset=windows-1252">
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To punish me for my contempt for authority, fate made me an
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authority myself"</i></font><br>
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Albert Einstein<br>
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</center>
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<img src="netbar.gif" height="40" align="middle" width="100%"> <br>
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<ul>
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</ul>
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<ul>
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<li>An electric dipole consists of two point charges of equal
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magnitude, but opposite sign, separated by a short distance.</li>
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</ul>
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<ul>
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<li>The dipole is electrically neutral, but due to the
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separation of its charges gives rise to an electric field in its
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vicinity.</li>
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</ul>
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<div align="center"><img alt="electric dipole" src="elec_dipole.jpg"
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height="347" width="461"><br>
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<div align="left">
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<ul>
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<li>The electric field at the "field point" is given by
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<b>E</b> = <b>E</b><sub>+q</sub> + <b>E</b><sub>-q</sub>.
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Note that in adding the two electric fields the y-component
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cancels leaving only an x-component given by,</li>
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</ul>
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<div align="center"><img alt="elec dipole eqn1"
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src="elec_dipole_eqn1.jpg" height="55" width="261"><br>
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<blockquote>
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<div align="left">where R is the distance from the centre of
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the dipole to the field point and the approximation is
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valid when r and R are almost equal. In this case
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the dimension of the dipole (a) is small compared to the
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field point distance.<br>
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</div>
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</blockquote>
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<div align="left">
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<ul>
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<li>p (=2aq) is called the electric dipole moment.
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It's actually a vector pointing from the negative to the
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positive charge in the dipole so that,</li>
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</ul>
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<div align="center"><img alt="elec dipole eqn 2"
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src="elec_dipole_eqn2.jpg" height="59" width="126"><br>
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<div align="left">
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<ul>
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<li><img alt="hot" src="hot.gif" height="43"
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align="middle" width="79">Many molecules have
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charge distributions which can be approximated as an
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electric dipole, water being one of the most common.</li>
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</ul>
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<div align="center"><img alt="water molecule"
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src="elec_water-molecule-and-dipole-moment.jpg"
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height="214" width="603"><br>
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</div>
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<ul>
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</ul>
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</div>
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</div>
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</div>
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</div>
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<ul>
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</ul>
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</div>
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</div>
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<div style="text-align: left;"><img src="netbar.gif" height="40"
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width="100%"> </div>
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<center><br>
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<span style="font-size: 12pt; font-family: "Times New
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Roman";"><span style="color: rgb(255, 0, 0); font-style:
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italic;">"How many Astronomers does it take to change a light
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bulb ?<br>
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None, astronomers prfeer the dark"</span></span><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"> </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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