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Re: Surface charge distribution



Both the replies agree that the charge distribution on the outer surface
will be uniform. However, I still have some questions:

1. If the point charge inside is +q will the total charge on the outer
surface be +q (and the charge on the cavity wall be -q)?

2. Assume that the point charge is close to the cavity surface. Now if
we increase the radius of the sphere (keeping the point charge at the
same distance from the cavity surface) the charge density on the outer
surface will decrease (right?) When the radius becomes infinity the part
of conducting sphere close to the point charge becomes a conducting
plate. The E-field on the other side of the plate will become ZERO
because the charge density on the plate will be zero! Is that correct?

Hasan Fakhruddin
Instructor of Physics
The Indiana Academy for Science, Mathematics, and Humanities
BSU
Muncie, IN 47306
E-mail: hfakhrud@bsu.edu


-----Original Message-----
From: Spagna Jr., George [mailto:gspagna@RMC.EDU]
Sent: Wednesday, December 04, 2002 7:49 AM
To: PHYS-L@lists.nau.edu
Subject: Re: Surface charge distribution

Hasan asks:

-----Original Message-----
From: Fakhruddin, Hasanbhai [mailto:hfakhrud@BSU.EDU]
Sent: Tuesday, December 03, 2002 7:28 PM
To: PHYS-L@lists.nau.edu
Subject: Surface charge distribution


Hello Everyone!

Need help with the following conceptual problem:

A conducting shell is initially neutral. A point charge +q is place=
d
OFF CENTER inside the cavity. Is the charge induced on its outer
surface symmetric or asymmetric? =20

Thanks,

Hasan Fakhruddin

Use Gauss's law to convince yourself that the charge on the outer sur=
face is uniformly distributed. (Conducting shell does not support an=
y electric field, so the outer surface "knows nothing" about the deta=
ils of the interior charge distribution.) The induced surface charge=
on the inner surface of the shell is not uniformly distributed.

********************************************
"My idea of an agreeable person is a=20
person who agrees with me."=20
--Benjamin Disraeli =20
********************************************
George Spagna
Department of Physics
Randolph-Macon College
P.O. Box 5005
Ashland, VA 23005-5505
phone: (804) 752-7344 =20
FAX (804) 752-4724
e-mail: gspagna@rmc.edu
http://www.rmc.edu