Charge on the surface of a sphere induced by a charge inside

In summary, the author is having trouble convincing himself that a charge located anywhere inside a conducting sphere will create an induced charge on the surface of the sphere with an electric field that is completely uniform. This doesn't make much sense to him.
  • #1
DivergentSpectrum
149
15
Im having trouble convincing myself that a charge located anywhere inside a conducting sphere will create an induced charge on the surface of the sphere with an electric field that is completely uniform. This doesn't make much sense to me.

Also same with how the electric field inside solid conductors is zero, but to a lesser degree(i get the idea that the induced charge will cancel out the initial field, but I am still kinda unsatisfied)

Do i just have to deal with it and go on until i get into more advanced stuff, or is there some kinda explanation/proof for it?
 
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  • #3
The excess electrons repel each other, so they want to get as far away from each other as possible. To do this they move to the surface of the conductor.
I guess this makes sense if the charge of a conductor is negative, but if the charge is positive does that mean protons are moving to the surface?
the charge in a hollow sphere explanation didnt make much sense either
 
  • #4
No, I think the positive charge causes the electrons to move inward leaving a more positive charge on the outside.
 
  • #5
still doesn't help me much. the page you showed me was pretty much the same explanation that griffiths introduction to electrodynamics gave. Oh well I am moving on as I am guessing the only way this could be proven is by studying the quantum mechanics of the individual atoms.
I hate how physics can't be approached in a "theorem by theorem" or even an axiom by axiom approach
 
  • #6
Have you ever noticed those spheres on charge bleeder 'lightning rods', what do you imagine they are doing, or do you think they're just decorative?
 
  • #7
Hmm, i tried looking for some kind of designs for them but couldn't find any.
Also, a (somewhat) unrelated item:
I was playing around with a program i made that numerically calculates the e field due to a surface charge, and i found that on the surface itself the e field is tangent to the surface. I understand that on the surface the e field will be approaching zero. (while out side it will be inverse square proportional in distance to the center of the sphere)
but this got me thinking, what is the e field ON the surface itself?
 

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  • #8
also, i used the surface of a torus (with uniform charge density)
the first photo shows the outside of the torus which looks right, but inside the E field inside is clearly not zero.
does this mean i did something wrong?
 

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Related to Charge on the surface of a sphere induced by a charge inside

1. What is the equation for calculating the charge on the surface of a sphere induced by a charge inside?

The equation for calculating the charge on the surface of a sphere induced by a charge inside is Q = (4πε0εra3)/r2, where Q is the induced charge, ε0 is the permittivity of free space, εr is the relative permittivity of the material, a is the radius of the sphere, and r is the distance from the center of the sphere to the charge inside.

2. How does the charge on the surface of the sphere change with increasing distance from the center of the sphere?

The charge on the surface of the sphere decreases with increasing distance from the center of the sphere. This is because the electric field strength decreases with distance, and the induced charge is directly proportional to the electric field strength.

3. Can the charge on the surface of the sphere be negative?

Yes, the charge on the surface of the sphere can be negative. This can occur if the charge inside the sphere is negative or if the relative permittivity of the material is less than 1. In this case, the induced charge will be negative, indicating an opposite polarity to the charge inside.

4. How does the relative permittivity of the material affect the charge on the surface of the sphere?

The relative permittivity of the material affects the charge on the surface of the sphere by changing the strength of the electric field inside the sphere. A higher relative permittivity will result in a stronger electric field and therefore a larger induced charge on the surface of the sphere.

5. Is the charge on the surface of the sphere affected by the size of the charge inside?

Yes, the charge on the surface of the sphere is affected by the size of the charge inside. As the charge inside increases, the strength of the electric field increases, resulting in a larger induced charge on the surface of the sphere. However, the distance between the charge inside and the center of the sphere also plays a role in the calculation of the induced charge.

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