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Subject: Electric circuits : BASIC CONCEPTS OF ELECTRICITY
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<LI><A title=3D"Page 1: Static electricity"=20
href=3D"http://www.allaboutcircuits.com/vol_1/chpt_1/1.html">Static=20
electricity</A>
<LI><A title=3D"Page 2: Conductors, insulators, and electron flow"=20
=
href=3D"http://www.allaboutcircuits.com/vol_1/chpt_1/2.html">Conductors, =
insulators, and electron flow</A>
<LI><A title=3D"Page 3: Electric circuits"=20
href=3D"http://www.allaboutcircuits.com/vol_1/chpt_1/3.html">Electric=20
circuits</A>
<LI><A title=3D"Page 4: Voltage and current"=20
href=3D"http://www.allaboutcircuits.com/vol_1/chpt_1/4.html">Voltage =
and=20
current</A>
<LI><A title=3D"Page 5: Resistance"=20
=
href=3D"http://www.allaboutcircuits.com/vol_1/chpt_1/5.html">Resistance</=
A>
<LI><A title=3D"Page 6: Voltage and current in a practical circuit"=20
href=3D"http://www.allaboutcircuits.com/vol_1/chpt_1/6.html">Voltage =
and current=20
in a practical circuit</A>
<LI><A title=3D"Page 7: Conventional versus electron flow"=20
=
href=3D"http://www.allaboutcircuits.com/vol_1/chpt_1/7.html">Conventional=
versus=20
electron flow</A>
<LI><A title=3D"Page 8: Contributors"=20
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<LI><A=20
=
href=3D"http://www.allaboutcircuits.com/worksheets/semicon.html">Electric=
al=20
conduction in semiconductors</A>
<LI><A =
href=3D"http://www.allaboutcircuits.com/worksheets/igfet.html">Insulated =
gate field-effect transistors</A></LI></UL><BR><B>Recently Viewed:</B>
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<H1>Electric circuits</H1>
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<P>You might have been wondering how electrons can continuously flow in =
a=20
uniform direction through wires without the benefit of these =
hypothetical=20
electron Sources and Destinations. In order for the =
Source-and-Destination=20
scheme to work, both would have to have an infinite capacity for =
electrons in=20
order to sustain a continuous flow! Using the marble-and-tube analogy, =
the=20
marble source and marble destination buckets would have to be infinitely =
large=20
to contain enough marble capacity for a "flow" of marbles to be =
sustained.=20
</P><A name=3DCircuit></A>
<P>The answer to this paradox is found in the concept of a =
<I>circuit</I>: a=20
never-ending looped pathway for electrons. If we take a wire, or many =
wires=20
joined end-to-end, and loop it around so that it forms a continuous =
pathway, we=20
have the means to support a uniform flow of electrons without having to =
resort=20
to infinite Sources and Destinations: </P>
<P><IMG src=3D"http://sub.allaboutcircuits.com/images/00012.png"> </P>
<P>Each electron advancing clockwise in this circuit pushes on the one =
in front=20
of it, which pushes on the one in front of it, and so on, and so on, =
just like a=20
hula-hoop filled with marbles. Now, we have the capability of supporting =
a=20
continuous flow of electrons indefinitely without the need for infinite =
electron=20
supplies and dumps. All we need to maintain this flow is a continuous =
means of=20
motivation for those electrons, which we'll address in the next section =
of this=20
chapter. </P>
<P>It must be realized that continuity is just as important in a circuit =
as it=20
is in a straight piece of wire. Just as in the example with the straight =
piece=20
of wire between the electron Source and Destination, any break in this =
circuit=20
will prevent electrons from flowing through it: </P>
<P><IMG src=3D"http://sub.allaboutcircuits.com/images/00013.png"> </P>
<P>An important principle to realize here is that <I>it doesn't matter =
where the=20
break occurs</I>. Any discontinuity in the circuit will prevent electron =
flow=20
throughout the entire circuit. Unless there is a continuous, unbroken =
loop of=20
conductive material for electrons to flow through, a sustained flow =
simply=20
cannot be maintained. </P>
<P><IMG src=3D"http://sub.allaboutcircuits.com/images/00014.png"> </P>
<UL>
<LI><B>REVIEW:</B>=20
<LI>A <I>circuit</I> is an unbroken loop of conductive material that =
allows=20
electrons to flow through continuously without beginning or end.=20
<LI>If a circuit is "broken," that means its conductive elements no =
longer=20
form a complete path, and continuous electron flow cannot occur in it. =
<LI>The location of a break in a circuit is irrelevant to its =
inability to=20
sustain continuous electron flow. <I>Any</I> break, <I>anywhere</I> in =
a=20
circuit prevents electron flow throughout the circuit. </LI></UL>
<DIV class=3Dbotnav align=3Dcenter><A title=3D"Discuss this topic on our =
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