From: Geoff Ruth (geoffreyruth@usa.net)
Date: Wed Nov 17 1999 - 20:49:51 PST
Message-ID: <19991118044951.16096.qmail@nwcst288.netaddress.usa.net> Date: 17 Nov 99 20:49:51 PST From: Geoff Ruth <geoffreyruth@usa.net> Subject: Re: [Re: pinhole polarity and charge]
Thanks to everyone who's written about this. I still have some questions.
It seems like it can't just be an "induced" separation of charges into
positive on one side of the stream and negative on the other. First, I don't
know how exactly this would work since covalent molecules don't share
electrons between molecules like metals do. But putting this aside, nonpolar
molecules like CCl4 should also show the same attraction since nonpolar
molecules can show an induced charge.
I like Marc's explanation a lot, although my physics isn't good enough to
actually slog through the math and see if the numbers come out right. Has
anyone else done these calculations or seen the results?
Assuming that it is a difference in electrical force due to the separation of
the partial charges, then it seems like a molecule with polar bonds but no net
dipole moment should still be attracted to the wand. Consider carbon
tetrachloride:
Cl
|
Cl - C - Cl
|
Cl
Because one of the C-Cl bonds is closer to the stream of water, it will
experience a greater force than the other ones (since the electrical field
falls off). Therefore, it should be either attracted or repelled since the
dipole in the closer C-Cl creates a greater force than the other bonds.
Consequently, even a nonpolar molecule should be affected by the wand. I don't
think the result would be as noticeable as with a polar molecule, but it
should still be there.
Is my logic right?
Again, thanks.
-Geoff
> Induced charge has always been my explanation too. Both positively charged
> and negatively charged objects will divert the stream toward the object.
> I've done this many times. Maybe this isn't exactly induced charge in the
> sense that charges actually move. The water molecule, being polar, could
> rotate a bit I would think.
>
> Rich Lohman
>
> >My guess is that the water stream has a polarity induced in it, such that
> >it becomes a bit positive near the rod and negative on the other side;
> >there are lots of charges in water and these can be influenced to move
> >somewhat. It is analagous to that same rod picking up a piece of neutral
> >paper. since the positive side is closer than the negative one, it gets
> >attracted to the rod. At least this is my guess. eiger
> >
> >
> >>Many high school and college chemistry textbooks show a picture of how a
> >>stream of a polar liquid falling will be deflected by a charge wand.
> >>Typically, they show liquid falling from a buret and being attracted to a
> >>plastic rod, which has a negative charge on it.
> >>
> >>I've been trying to figure out exactly why this happens, without luck.
Help?
> >>
> >>-Geoff Ruth
> >
> >Steven Eiger, Ph.D.
> >
> >Departments of Biology and the WWAMI Medical Education Program
> >Montana State University - Bozeman
> >Bozeman, MT 59717-3460
____________________________________________________________________
Get free email and a permanent address at http://www.netaddress.com/?N=1
This archive was generated by hypermail 2b29 : Thu Oct 19 2000 - 11:09:53 PDT