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