A charged capacitor has a potential difference when it is just "sitting
around" A battery has no potential difference unless there is a current
through it. IF I take a capacitor and drop its temperature to 5 K say, it
will still have a charge to discharge. A battery at 5 K is dead, the
reaction will not happen. In a capacitor I can discharge as fast as I want
depending on the circuit, a battery can only deliever as fast as the
reaction can go (a cold battery delievers lower currents than hot
batteries). A capacitor's potential difference changes as the the charge
changes. A battery delievers a specific potential difference is a given
circuit as long as there are chemicals left to react. So if you need a
quick jolt delivered at a specific time, use a capacitor. If you need a
steady current over a long time use a battery.
David
-----Original Message-----
From: Tina Fanetti [mailto:FanettT@WITCC.COM]
Sent: Wednesday, February 12, 2003 12:18 PM
To: PHYS-L@lists.nau.edu
Subject: Re: Batteries and Capacitors
For almost all practical purposes, a battery can be
thought of as a capacitor with a huuuuge capacitance
and crummy high-frequency performance.<<<
But why? We were talking about defilbilators and how thay have capac=
itors in them. Why can't they just use a batteries in the device?
Tina
Tina Fanetti
Physics Instructor
Western Iowa Technical Community College
4647 Stone Ave
Sioux City IA 51102
712-274-8733 ext 1429