How to uniformly charge an insulating sphere?

In summary: What problem?What does excess charge tend to do?What is an insulator?What is the solution?What is the book's title?In summary, the book discusses a problem of finding an electric field that evenly distributes electric charge throughout the volume of an insulating sphere. The book suggests two methods for achieving this goal: using a charged 'wand' to touch the sphere's surface at all points or putting the sphere in a vacuum and bombarding it with electrons. Neither of these methods are perfect, as the charge is only spread over the surface of the sphere. The book also mentions a potential method for charging the sphere throughout its entirety; covering it with a plastic coating and then ripping it off
  • #1
amiras
65
0
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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  • #2
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.
 
  • #3
is it not possible to uniformly heat the "insulating sphere" as to release conduction electrons?
 
  • #4
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.
 
  • #5
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.
 
  • #6
You're a hard man to please.
Could your big sphere be made of many smaller spheres?
 
  • #7
I would use something more space-filling, like cubes (with special parts for the surface?), but that is possible, sure.
 
  • #8
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.
 
  • #9
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?
 

1. What is the process of uniformly charging an insulating sphere?

The process of uniformly charging an insulating sphere involves using an external electric field to transfer electrons from one side of the sphere to the other, resulting in a balanced distribution of charge on the surface.

2. How do you create an external electric field to charge the sphere?

An external electric field can be created by using a charged object, such as a charged rod or plate, near the insulating sphere. The charged object will induce a charge on the surface of the sphere, resulting in a uniform distribution of charge.

3. Can an insulating sphere be uniformly charged without an external electric field?

No, an insulating sphere cannot be uniformly charged without an external electric field. Due to the insulating nature of the sphere, the charge cannot move freely and an external electric field is required to redistribute the charge.

4. What factors can affect the uniformity of the charge on the insulating sphere?

The size of the insulating sphere, the strength of the external electric field, and the material of the sphere can all affect the uniformity of the charge. A larger sphere may require a stronger electric field to achieve uniform charge, and different materials may have different levels of conductivity.

5. Is there a limit to how uniformly an insulating sphere can be charged?

Yes, there is a limit to how uniformly an insulating sphere can be charged. As the size of the sphere increases, it becomes more difficult to achieve a perfectly uniform distribution of charge. Additionally, imperfections in the material can also affect the uniformity of the charge.

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