How to uniformly charge an insulating sphere?

  • Thread starter amiras
  • Start date
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?
 
33,396
9,113
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.
 
88
0
is it not possible to uniformly heat the "insulating sphere" as to release conduction electrons?
 

sophiecentaur

Science Advisor
Gold Member
23,557
3,961
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.
 
33,396
9,113
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.
 

sophiecentaur

Science Advisor
Gold Member
23,557
3,961
You're a hard man to please.
Could your big sphere be made of many smaller spheres?
 
33,396
9,113
I would use something more space-filling, like cubes (with special parts for the surface?), but that is possible, sure.
 

Vanadium 50

Staff Emeritus
Science Advisor
Education Advisor
23,238
5,574
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.
 

sophiecentaur

Science Advisor
Gold Member
23,557
3,961
Perfect 'enough'?
 
1,506
17
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?
 

Related Threads for: How to uniformly charge an insulating sphere?

Replies
3
Views
2K
Replies
9
Views
478
Replies
1
Views
9K
Replies
2
Views
1K
  • Posted
Replies
1
Views
2K
  • Posted
Replies
3
Views
1K
Replies
3
Views
559

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top