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GR0177 #8
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Problem
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This problem is still being typed. |
Electromagnetism }Conductors
A conductor has the magical mystical property of inducing the exact opposite charge of a nearby charge. One has all the electrons in the conductor moving towards the positive charge placed outside Q. A net negative charge of -Q is induced.
(Also, one recalls that this was the assumption made in finding the potential of this setup using the Method of Images---the charged plane was assumed to have a charge density  .)
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Alternate Solutions |
sonnb
2009-01-27 20:29:35 | The question should read "What is the total charge induced on the top face of the plane". Otherwise, there should be an induced charge on the bottom face of the plane of +Q. Then the answer should be (C). |  |
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Comments |
wittensdog
2009-10-08 19:10:38 | Note very carefully that the plane needs to be GROUNDED. If it is not grounded, there is no source of charge that the plane can draw from in order to gain a net charge. This fact is used in the method of images, since we require the plane to go to zero potential.
However, even if the plane is insulated, it could still have its charge move around and gain a surface charge. But the net charge on the plane would not be able to change from zero.
If the plane is held at some non-zero potential, then it gets more complicated. |  | sonnb
2009-01-27 20:29:35 | The question should read "What is the total charge induced on the top face of the plane". Otherwise, there should be an induced charge on the bottom face of the plane of +Q. Then the answer should be (C).
jmason86
2009-07-14 19:51:49 |
My EM is a little rusty, but I think that the +Q charge that is induced on the bottom half gets dumped by way of the grounding that the problem states.
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beradg07
2010-07-11 02:59:05 |
But the plane is a 2 dimensional object so there is no such thing as a top and bottom face, they are the same face. Thus the question is correct as stated.
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2008-11-05 20:32:19 | So, if magic and mystery aren't your thing... (and if you're a physicist, they shouldn't be), then check out the method of image charges which explains how to do these types of problems.
http://en.wikipedia.org/wiki/Method_of_image_charges | | rajendratimilsina
2008-10-23 18:09:41 | I am agree with this solution because conductor has a special property of inducing charge nearby the given charge. | |
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