117 lines
4.4 KiB
HTML
117 lines
4.4 KiB
HTML
|
<!DOCTYPE html PUBLIC "-//w3c//dtd html 4.0 transitional//en">
|
||
|
|
<html>
|
||
|
|
<head>
|
||
|
|
<meta http-equiv="Content-Type" content="text/html;
|
||
|
|
charset=windows-1252">
|
||
|
|
<meta name="GENERATOR" content="Mozilla/4.7 [en] (X11; U; OSF1 V4.0
|
||
|
|
alpha) [Netscape]">
|
||
|
|
<meta name="Author" content="C. L. Davis">
|
||
|
|
<title>Electricity - Electric Dipole - Physics 299</title>
|
||
|
|
</head>
|
||
|
|
<body style="color: rgb(0, 0, 0); background-color: rgb(255, 255,
|
||
|
|
255);" link="#0000ee" alink="#ff0000" vlink="#551a8b">
|
||
|
|
<center>
|
||
|
|
<h1> <img src="ULPhys1.gif" height="50" align="texttop"
|
||
|
|
width="189"></h1>
|
||
|
|
</center>
|
||
|
|
<center>
|
||
|
|
<h1>Electric Field due to a Dipole<br>
|
||
|
|
</h1>
|
||
|
|
</center>
|
||
|
|
<center><img src="celticbar.gif" height="22" width="576"><br>
|
||
|
|
<br>
|
||
|
|
<font color="#ff0000"><i>"</i></font><font color="#ff0000"><i>
|
||
|
|
<meta http-equiv="content-type" content="text/html;
|
||
|
|
charset=windows-1252">
|
||
|
|
To punish me for my contempt for authority, fate made me an
|
||
|
|
authority myself"</i></font><br>
|
||
|
|
Albert Einstein<br>
|
||
|
|
</center>
|
||
|
|
<img src="netbar.gif" height="40" align="middle" width="100%"> <br>
|
||
|
|
<ul>
|
||
|
|
</ul>
|
||
|
|
<ul>
|
||
|
|
<li>An electric dipole consists of two point charges of equal
|
||
|
|
magnitude, but opposite sign, separated by a short distance.</li>
|
||
|
|
</ul>
|
||
|
|
<ul>
|
||
|
|
<li>The dipole is electrically neutral, but due to the
|
||
|
|
separation of its charges gives rise to an electric field in its
|
||
|
|
vicinity.</li>
|
||
|
|
</ul>
|
||
|
|
<div align="center"><img alt="electric dipole" src="elec_dipole.jpg"
|
||
|
|
height="347" width="461"><br>
|
||
|
|
<div align="left">
|
||
|
|
<ul>
|
||
|
|
<li>The electric field at the "field point" is given by
|
||
|
|
<b>E</b> = <b>E</b><sub>+q</sub> + <b>E</b><sub>-q</sub>.
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
Note that in adding the two electric fields the y-component
|
||
|
|
cancels leaving only an x-component given by,</li>
|
||
|
|
</ul>
|
||
|
|
<div align="center"><img alt="elec dipole eqn1"
|
||
|
|
src="elec_dipole_eqn1.jpg" height="55" width="261"><br>
|
||
|
|
<blockquote>
|
||
|
|
<div align="left">where R is the distance from the centre of
|
||
|
|
the dipole to the field point and the approximation is
|
||
|
|
valid when r and R are almost equal. In this case
|
||
|
|
the dimension of the dipole (a) is small compared to the
|
||
|
|
field point distance.<br>
|
||
|
|
</div>
|
||
|
|
</blockquote>
|
||
|
|
<div align="left">
|
||
|
|
<ul>
|
||
|
|
<li>p (=2aq) is called the electric dipole moment.
|
||
|
|
It's actually a vector pointing from the negative to the
|
||
|
|
positive charge in the dipole so that,</li>
|
||
|
|
</ul>
|
||
|
|
<div align="center"><img alt="elec dipole eqn 2"
|
||
|
|
src="elec_dipole_eqn2.jpg" height="59" width="126"><br>
|
||
|
|
<div align="left">
|
||
|
|
<ul>
|
||
|
|
<li><img alt="hot" src="hot.gif" height="43"
|
||
|
|
align="middle" width="79">Many molecules have
|
||
|
|
charge distributions which can be approximated as an
|
||
|
|
electric dipole, water being one of the most common.</li>
|
||
|
|
</ul>
|
||
|
|
<div align="center"><img alt="water molecule"
|
||
|
|
src="elec_water-molecule-and-dipole-moment.jpg"
|
||
|
|
height="214" width="603"><br>
|
||
|
|
</div>
|
||
|
|
<ul>
|
||
|
|
</ul>
|
||
|
|
</div>
|
||
|
|
</div>
|
||
|
|
</div>
|
||
|
|
</div>
|
||
|
|
<ul>
|
||
|
|
</ul>
|
||
|
|
</div>
|
||
|
|
</div>
|
||
|
|
<div style="text-align: left;"><img src="netbar.gif" height="40"
|
||
|
|
width="100%"> </div>
|
||
|
|
<center><br>
|
||
|
|
<span style="font-size: 12pt; font-family: "Times New
|
||
|
|
Roman";"><span style="color: rgb(255, 0, 0); font-style:
|
||
|
|
italic;">"How many Astronomers does it take to change a light
|
||
|
|
bulb ?<br>
|
||
|
|
None, astronomers prfeer the dark"</span></span><br>
|
||
|
|
<br>
|
||
|
|
<img src="celticbar.gif" height="22" width="576"> <br>
|
||
|
|
|
||
|
|
<p><i>Dr. C. L. Davis</i> <br>
|
||
|
|
<i>Physics Department</i> <br>
|
||
|
|
<i>University of Louisville</i> <br>
|
||
|
|
<i>email</i>: <a href="mailto:c.l.davis@louisville.edu">c.l.davis@louisville.edu</a>
|
||
|
|
<br>
|
||
|
|
</p>
|
||
|
|
<p><img src="header-index.gif" height="51" width="92"> </p>
|
||
|
|
</center>
|
||
|
|
<p><br>
|
||
|
|
</p>
|
||
|
|
</body>
|
||
|
|
</html>
|