Conducting sphere connected to the ground

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  • #1
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Homework Statement


attachment.php?attachmentid=58611&d=1368161323.jpg




Homework Equations





The Attempt at a Solution


The ground is at zero potential. Hence, the sphere should be also at zero potential. The net charge should be zero, so a charge of -Q should flow from the ground to sphere. But this is wrong. :confused:
 

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  • #2
Simon Bridge
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Hint:
1. wire is connected to inner surface.
2. it asks for charge moved from the sphere and to the ground.

The text says "sphere radius r" but the diagram shows a sphere inner radius r and an unspecified outer radius. Does it make a difference?
 
  • #3
SammyS
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Homework Statement


(see attachment)

Homework Equations



The Attempt at a Solution


The ground is at zero potential. Hence, the sphere should be also at zero potential. The net charge should be zero, so a charge of -Q should flow from the ground to sphere. But this is wrong. :confused:
[ IMG]https://www.physicsforums.com/attachment.php?attachmentid=58610&d=1368159359[/PLAIN]

One could state the result as you have, but that wasn't what the question asked.
 
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  • #4
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Hint:
1. wire is connected to inner surface.
2. it asks for charge moved from the sphere and to the ground.
The inner surface has no charge according to the figure. So a charge of +Q should flow to the ground for a negative charge of -Q to appear and bring the potential down to zero?

Simon Bridge[/quote said:
The text says "sphere radius r" but the diagram shows a sphere inner radius r and an unspecified outer radius. Does it make a difference?
No idea about this. :confused:
 
  • #5
ehild
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The problem asks the charge flowing from the sphere to the ground. The whole sphere is at the same potential (both outside and inside) Current flows if there is potential difference across the resistance, between the sphere and the ground. Till there are charges on the sphere, there is potential difference. That negative charge you speak about does not appear, but the positive disappears:tongue2:

ehild.
 
  • #6
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The problem asks the charge flowing from the sphere to the ground. The whole sphere is at the same potential (both outside and inside) Current flows if there is potential difference across the resistance, between the sphere and the ground. Till there are charges on the sphere, there is potential difference. That negative charge you speak about does not appear, but the positive disappears:tongue2:

ehild.
Got it, thanks ehild! :smile:
 

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