Sometimes you can use a symmetry argum= ent to show that the dipole moment is zero. But in general? Not tha= t I know of. (I haven’t seen Kumar’s reply).

Example: The arrangement:

+ - - +

- + + -

+ - - + =

has a center of symmetry, and so must = have a zero dipole moment; any dipole-moment vector of positive length would be incompatible with the symmetry.

--David

From: owner-chemistry|,|ccl.net [mailto:owner-chemistry|,|ccl.net]
Sent: Monday, July 23, 2007 = 12:36 PM
To: Shobe, David
Subject: CCL: Arranging elec= tric charges to manage Dipole moment ..????

Thanks for the reply.

Isn't it possible to say the syste= m has net dipole or not just seeing the arrangement of charges.? Without calculat= ing this components??? As Kumar replied me.

Thanks

REAZ

"Shobe, David David.Shobe-.-sud-chemie.com" <owner-chemistry{=3D}ccl.net> wrote:

Sent to CCL by: "Shobe, David" [David.Shobe{}sud-chemie.com]
REAZ,

You can calculate the x component of the dipole moment as follows:
calculate the sum over charges .SIGMA. qi xi where qi is the magnitude
of the i'th charge and (xi, yi, zi) is the position of the i'th charge.
All those i's are supposed to be subscripts. The y and z components of
the dipole moment are calculated analogously.

It may appear at first that this formula is dependent on the choice of
origin, but it really isn't, as long as the ensemble of charges is
neutral overall. Changing the origin will change each xi in the sum,
but the changes will cancel out for positive and negative charges.

For a continuous charge density, one replaces the sums with integrals.

Regards,
--David Shobe

-----Original Message-----
> From: owner-chemistry[#]ccl.net [mailto:owner-chemistry[#]ccl.net]
Sent: Friday, July 20, 2007 9:23 PM
To: Shobe, David
Subject: CCL: Arranging electric charges to manage Dipole moment ..????

Sent to CCL by: "Reaz Uddin" [riaasuddin : yahoo.com]
Hi,
Can anybody explain me the arrangement of charges with respect to the
dipole moment. I mean, How can I arrange a small number(lets say 8 or
12) of charges where I could find at certain arrangement no dipole
moment (like they cancel out each other) or at certain arrangement they
show the dipole moment. Take an example of 12 charges in which 4 are +
and 4 are -.
I would say I arranged them in the following manner:
+-+-
++--
+--+
Does the above arrangement show dipole moment,? if yes then please
arrange it in a way so that they dont show any dipole moment.
Hope I'd get an explanatory answer in this regard.
Thanks in advance. I appreciate you guys.
REAZhttp://www.ccl.net/cgi-bin/ccl/send_ccl_messagehttp://www.ccl.net/chemi= stry/sub_unsub.shtmlhttp://www.ccl.net/spammers.txtThis e-mail message may contain confidential and / or privileged information. If= you are not an addressee or otherwise authorized to receive this message, you should not use, copy, disclose or take any action based on this e-mail or a= ny information contained in the message. If you have received this material in error, please advise the sender immediately by reply e-mail and delete this message.
Thank you.

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