From: Marc Afifi (mafifi@redshift.com)
Date: Mon Nov 15 1999 - 05:55:34 PST
Message-ID: <383010CE.635D@redshift.com> Date: Mon, 15 Nov 1999 13:55:34 +0000 From: Marc Afifi <mafifi@redshift.com> Subject: Re: pinhole polarity and charge
Regarding stream of water attracted to charged rod.
My understanding of this phenomenon is that the attraction occurs due to
the polarity of the water molecule which is caused by its bent shape
(polar bond dipole moments don't cancel).
_
O
/ \
H H
+
The strongly polar bond between the hydrogen and oxygen atoms within the
water molecule in concert with the two unbonded pairs of electrons on
the oxygen atom produce the dipolarity of the water molecule. Therefore,
tests with a positive rod or negative rod result in the same observation
-- attraction. Since the water molecules are free to rotate, the
negative side turns toward the positive rod and is attracted. Likewise,
the positive side turns toward the negative rod and is attracted.
I don't think we're talking about induced charge here. If we were, then
wouldn't we observe the same phenomenon using a stream of nonpolar oil
molecules? Try it. See what happens.
By the way, I have found that this demonstration is particularly
dramatic if you use styrofoam rubbed with wool. The styrofoam seems to
be able to store a larger static charge than glass does. Always good for
oohs and aahs.
-Marc
-- Marc Afifi Physics, Chemistry and Marine Science Pacific Grove High School 615 Sunset Dr. Pacific Grove, CA, 93950 http://www.pghs.org/staff/afifi/d5hp.html(831) 646-6590 ext. 223
Favorite Oakland Raiders Motto: "Just When Baby?"
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