Charges on an Outer & Inner Shell w/ -5.0E-6C Center

[mollyanne15]

A shell with a charge of -5.0E-6 C at the center. What will the charge be on the inner surface of the shell? The outer?

 

[Shooting Star]

Is the shell made of a conducting material?

 

[mollyanne15]

It doesn't say. The first part of the question says, "A thin spherical shell of radius 15.0cm with total charge of 33.0E-6 C distributed uniformly on its surface."
If there was a ball of charge of -5.0E-6...

 

[Shooting Star]

I presume it's a conductor, since the charge on the inner surface changes with the introduction of charge in the centre. So, what do you know about induced charges on the inside surface of a conductor?

 

[mollyanne15]

I would think that the charge on the inner shell would be +5E-6, so would that make the outer 0 to keep an overall neutral charge on the shell?

 

[Shooting Star]

If there's an induced charge of +q on the inside, where's the -q gone, to keep the shell have overall zero charge? How can a charge of 0 on the outer surface keep it neutral, as you've written?

 

[mollyanne15]

Because the charge in the center is (-), that would make the charge closest to it (inner) opposite in sign (+5E-6) leaving the outer surface zero.

 

[Shooting Star]

The conductor was initially neutral. You've put -q at the centre, and saying that now there's +q on the inner surface and 0 on the outer surface, which makes the system overall neutral. How can that be, when you've introduced some -q in the system?

If +q is induced on the inner surface, there must be a -q somewhere to balance it.

 

[mollyanne15]

So would the outer surface also be +5E-6?

 

[Shooting Star]

-5E-6; -q at the centre, +q on the inner surface, and -q on the outer surface.