Electric field at a point within an infinite volume charge distribution

In summary, the conversation discusses the electric field dependency for infinite line, plane, and volume charge distributions. The speaker wonders if an infinite charge volume would have a linear dependency on r, but realizes they do not have the necessary calculus knowledge to work through it. They also speculate about the behavior of electric fields in higher dimensions. Ultimately, they decide to leave the question for now and focus on other topics.
  • #1
Villhelm
37
0
I started reading through "Electricity and Magnetism" by Purcell and came across the derivations for infinite line and infinite plane charge distributions and noticed the former has a 1/r dependency (on perpendicular distance from the wire) and a constant value for the plane.

Would an infinite charge volume have a linear dependency on r, eg constant*r?

I don't have the multivariable calculus knowledge to work this through myself to see, but this is just out of interest right now ...

I've thus far reasoned that this might be so by considering that E=0 at the center of the distribution (from symmetry) and then moving a distance r out from the center would produce a cuboid of charge, an infinite plane face and thickness r and thus the flux would be like taking the single variable integral of a bunch of infinite plane electric fields (which I assume have a constant electric field strength as in the book) from 0->r ... thus introducing a linear r dependency?

Is this ad hoc reasoning ok or am I way off?

I expect to cover the calculus sometime in the next few weeks anyway so I can hopefully form the equations up myself ... but this is bugging me since I thought about it first :(
 
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  • #2
unless you're considering the electric field in the 4-th dimension, the electric field for an infinite volume distribution has to be 0. An infinite charge volume would stretch out over the entire universe and the test charge would have to be inside the conducting material unless it was outside the universe (huh??) or in a higher dimension (huh??)
 
  • #3
No need to be flippant about it, I find that considering and trying to extend/generalise everything I come across even it if seems or is unphysical to be useful mental exercise.

So, my question becomes:

If there were 4 or more spatial dimensions, then would the above hold true?
 
  • #4
sorry if i came off as flippant, i was actually trying to be humorous (evidently, that failed)

im a student barely ahead of you so i have no clue about its behavior in 4d
 
  • #5
Ah, ok ... I read overtones on the (huh?) that were incorrect, sorry about that. :redface:

Anyway, there are bigger fish to fry at this time of year so I'll consider this effectively closed.
 

1. What is an electric field at a point within an infinite volume charge distribution?

The electric field at a point within an infinite volume charge distribution is the force per unit charge experienced by a charge placed at that point, due to the presence of the charges in the distribution. It is a vector quantity and is represented by the symbol E.

2. How is the electric field at a point within an infinite volume charge distribution calculated?

The electric field at a point within an infinite volume charge distribution can be calculated using the formula E = (k * Q) / r², where k is the Coulomb's constant, Q is the total charge in the distribution, and r is the distance from the point to the center of the distribution. Alternatively, it can also be calculated by summing up the contributions of individual charges in the distribution using the principle of superposition.

3. Does the electric field at a point within an infinite volume charge distribution vary with distance?

Yes, the electric field at a point within an infinite volume charge distribution varies with the distance from the center of the distribution. As the distance increases, the electric field decreases according to the inverse square law.

4. What is the direction of the electric field at a point within an infinite volume charge distribution?

The direction of the electric field at a point within an infinite volume charge distribution is always directed away from positive charges and towards negative charges. This direction can be determined using the principle of superposition or by considering the direction of the individual electric fields due to each charge in the distribution.

5. Can the electric field at a point within an infinite volume charge distribution be negative?

Yes, the electric field at a point within an infinite volume charge distribution can be negative if the point is located within a region of negative charges or if the electric field is directed towards negative charges. It is important to note that the magnitude of the electric field is always positive, while the direction can be either positive (away from positive charges) or negative (towards negative charges).

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