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A clearcut definition of Potential please

Matt Jones jonesmat at ohsu.edu
Tue Feb 9 13:05:48 EST 1999


In article <36BF0C1B.F79522A9 at mich.com> Michael Edelman, mje at mich.com
writes:
>Right. Think of it this way: You're standing on a large plateau at
>10,000'. You hold in your hand a 1 lb cannonball, 6' off the ground.
>
>You drop the cannonball.
>
>In a sense, you've dropped it from an altitude of 10,006 feet, but the
>actual potential energy that you could extract was only the difference
>between where it started (+10,006'), and where it ended up (+10,000').
>

I also like the gravitation/potential energy analogy. If you keep
thinking of potential as being "like" gravity, only with charge thrown
in, you probably won't get too confused. The equation governing how two
charges act on each other (Coulomb's Law) is in fact the same equation
governing how two masses act on each other (Newton's Law of Gravitation)
except it uses different variables (and of course, takes into account the
difference in charge). So many of the common sense things you expect
about gravity will also work when thinking of potential. It is worth
mentioning that potential difference IS NOT a force (even though everyone
talks about it as "the driving force"), and it is NOT energy. It is
associated with force and energy in the same way that height is
associated with the force of gravity and kinetic energy during a fall.
You wouldn't say that height is energy or force, so you shouldn't think
that potential is energy or force either. Consulting a high school or
higher physics text with a chapter on electromagnetism will help clarify
the issue, especially if you work through some problems.

Cheers,

Matt Jones



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