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Re: Batteries and Capacitors



To answer your question (below) as simply as possible .....

A capacitor essentially consists of two electrical conductors
separated by a dielectric.
When "charged" it actually stores a surplus of electrons in one of the
conductors and an equal number of unpaired positive charges at the other
end.
When the two outer terminals are shorted together. there is flow of
electroms
through the shorting wires until the uncharged condition of the capacitor

is obtained again.

A battery does not store electrons and protons separately in the same
manner as the capacitor. The battery only contains uncharged solid and
liquid chemicals. When the battery terminls are shorted. the chemicals
react somehow and produce an electric current that flows from one
terminal to
the other until the chemicals of the battery are exhausted.

For a much better explanation, instead of answering the student's
question yourself, tell her to find the answer in a library book or via
the
internet and report to the class next time for extra credit.

Herb Gottlieb from New York City
(Where students stop asking such questions if it means
that they have to do extra work themselves)
.........................................................................
................

On Wed, 12 Feb 2003 10:43:42 -0600 Tina Fanetti <FanettT@WITCC.COM>
writes:
'lo
In my calc based physics class, we are studying circuits and I
talked=
about batteries and capacitors. =20
I explained that a capacitor stored electrical energy..yadda yadda

One of my students then asked me what the difference between a
capaci=
tor and a battery is. I was like a capacitor stores energy, and a
ba=
ttery is a voltage source. =20

He then asked me why you would need a capacitor in the first place,
w=
hy not just use batteries. I was like you need to store charge for
s=
omethings and a battery can't do that.

It seems there is a piece in here that is important. He thinks
somet=
hing about the battery and the capacitor is the same and I am at a
lo=
ss to explain what that could not be or how to explain the
differenc=
es better.

My guess is that he thinks that a battery has charge and holds the
ch=
arge...

Thanks
Tina

Tina Fanetti
Physics Instructor
Western Iowa Technical Community College
4647 Stone Ave
Sioux City IA 51102
712-274-8733 ext 1429