A neutral conducting sphere and an insulating sphere....

[alexdr5398]

Homework Statement

Homework Equations

None

The Attempt at a Solution

My thinking was that the positively charged sphere would repel the electrons to the far side of the neutral sphere, creating a repulsive force between the two spheres until they touch and the charge is shared.

Since the one sphere is insulating, I'm guessing that means they wouldn't share the charge, but why do they attract each other?

 

[TSny]

My thinking was that the positively charged sphere would repel the electrons to the far side of the neutral sphere, ...

OK. When electrons accumulate on the far side, can you describe the charge distribution of the neutral sphere?

 

[alexdr5398]

OK. When electrons accumulate on the far side, can you describe the charge distribution of the neutral sphere?

The side closest the +ve charge sphere will be positively charged, since the free electrons will be reppeled to the other side.

Is it because the free electrons in +ve sphere will also be attracted the now positive side of the neutral sphere? So they attract?

 

[TSny]

Sorry, I misread your first argument. If the insulating sphere is positively charged, do the free electrons in the neutral sphere move to the far side or to the near side?

 

[alexdr5398]

Sorry, I misread your first argument. If the insulating sphere is positively charged, do the free electrons in the neutral sphere move to the far side or to the near side?

Oh, of course, they are attracted to the near side. :( What a dumb mistake.

I understand now thank you.

 

[TSny]

Oh, of course, they are attracted to the near side. :( What a dumb mistake.

I understand now thank you.

OK. But make sure you see the whole story. Electrons move to the near side. But that leaves the far side positively charged. So, although the insulating sphere will attract the negative charge that accumulates on the near side of the conducting sphere, it will repel the positive charge that accumulates on the far side. So, you still need to explain why the attraction is greater than the repulsion.

 

[alexdr5398]

OK. But make sure you see the whole story. Electrons move to the near side. But that leaves the far side positively charged. So, although the insulating sphere will attract the negative charge that accumulates on the near side of the conducting sphere, it will repel the positive charge that accumulates on the far side. So, you still need to explain why the attraction is greater than the repulsion.

Is it because the positive charges are less dense and farther away than the negative charges. The electrons all accumulate closest to the positive sphere and therefore create a larger attractive force than the +ve charges.

 

[TSny]

Is it because the positive charges are less dense and farther away than the negative charges. The electrons all accumulate closest to the positive sphere and therefore create a larger attractive force than the +ve charges.

Yes. The force is stronger on the negative charge because the negative charge is closer to the positively charge insulating sphere. Good.

 

[alexdr5398]

Yes. The force is stronger on the negative charge because the negative charge is closer to the positively charge insulating sphere. Good.

Thanks a lot for your help.