How to uniformly charge an insulating sphere?

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SUMMARY

The discussion centers on the challenge of uniformly charging an insulating sphere, specifically addressing the distribution of electric charge throughout its volume. Participants highlight that while excess charge typically migrates to surfaces, insulating materials prevent charge from leaving individual molecules. Various methods are proposed, including using an electron beam to bombard the sphere while rotating it, and applying a charged wand to touch the surface uniformly. However, these methods primarily affect surface charge rather than achieving a uniform volume charge distribution.

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amiras
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In my Physics book there was this problem of finding electric field produced by the sphere, such that electric charge is distributed uniformly throughout the volume of an insulating sphere.

I know that excess charge tends to distribute itself on the surfaces, but since this sphere is made from insulating materials excess charge cannot leave individual molecules to do so?

Anyway, how it is possible to charge an insulating sphere throughout the volume?
 
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Those spheres are just hypothetical objects - there are no perfect insulators, if you wait long enough the charge will be at the surface only.
You can place electrons at specific regions with electron beams, but I doubt that the result will give a uniform charge distribution.
 
is it not possible to uniformly heat the "insulating sphere" as to release conduction electrons?
 
Johnahh said:
is it not possible to uniformly heat the "insulating sphere" as to release conduction electrons?

You could take a charged 'wand' and touch the surface of the sphere at all points over its surface. Alternatively, you could put the sphere in a vacuum and bombard it with electrons whilst tumbling it at a steady rate. Electrons would then be spread (painted) over the surface. Of course, you would need to adjust the energy and focus of the electron beam because it would be deflected by electrons already on the surface. Woops - just read the previous post which says more or less the same thing.

What about covering the sphere with a plastic coating and ripping the coating off. You would then get a charge all over the surface as you do with a roll of cling film. That. I think, is a method that could actually deliver some sort of a practical result.
 
sophiecentaur said:
What about covering the sphere with a plastic coating and ripping the coating off. You would then get a charge all over the surface as you do with a roll of cling film. That. I think, is a method that could actually deliver some sort of a practical result.
As far as I know, those induced charges are quite unpredicable, and not constant.

In addition, it charges the surface only, not the full volume.
 
You're a hard man to please.
Could your big sphere be made of many smaller spheres?
 
I would use something more space-filling, like cubes (with special parts for the surface?), but that is possible, sure.
 
You're unhappy with perfectly insulating, but are fine with perfect spheres?

Like a lot of problems in physics, these are idealizations or approximations. Just like frictionless planes, massless and stretchless ropes, etc.
 
Perfect 'enough'?
 
  • #10
amiras said:
In my Physics book there was this problem of finding electric field produced by the sphere, such that electric charge is distributed uniformly throughout the volume of an insulating sphere.

I know that excess charge tends to distribute itself on the surfaces, but since this sphere is made from insulating materials excess charge cannot leave individual molecules to do so?

Anyway, how it is possible to charge an insulating sphere throughout the volume?

What physics book?
 

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