How Do You Calculate the Electric Field in a Finite Charged Plate?

In summary, the electric field causes a charge distribution on a thin sheet of metal. The electric field is created by the field from the two plates, which is inversely proportional to the field on the outside.
  • #1
Rib5
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0

Homework Statement


There is an electrical field causing a charge distribution of +Q and -Q on a thin square sheet of conductor with area A. Find the field


The Attempt at a Solution



I was wondering how you can find the electric field if you don't know the thickness of the thin metal sheet? I thought about using Gauss's law but I don't know over what surface you could find a constant E.
 
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  • #2
Assume that the charges are uniformly distributed over the surfaces of the conductor. (What's the field from a sheet of charge?) What field would such a charge distribution create in the space between them? What must be the actual field within the conductor? So what additional field must be present?
 
  • #3
Wouldn't the field inside the sheet be 0 since it is a conductor?
 
  • #4
Rib5 said:
Wouldn't the field inside the sheet be 0 since it is a conductor?
Right. The total field within the conducting sheet will be zero. What's the contribution from the surface charges?
 
  • #5
Alright I see where this is going. The field from the "two" plates creates a field equal and opposite to the electric field that is on the outside.

The thing that had me confused was that in the problem they give you the size of the plates (15cm), so I thought you can't assume they are infinite plates. But now I realize they just tell you that so you can get charge density.

Is the reason you can assume that the plates are infinite in size that they are so close together that any charge you put between would be so close to the plate compared to the size of the plate?

[[Edit]]

I solved the problem at least I'm pretty sure. I did it using the fact that the field away from an infinite plane is density/(2*Enot)

The other way I did it was using Gauss's Law and putting a box through the plane.Thanks for the help
 
Last edited:

1. What is meant by "field" in relation to charges?

The term "field" refers to the force exerted by a charged particle on other charged particles in its vicinity. It can also be described as the region of space where the effect of the charged particle's force can be felt.

2. How do you calculate the field from a single point charge?

To calculate the field from a single point charge, you can use the formula E = k*q/r^2, where E is the electric field, k is the Coulomb's constant, q is the charge of the particle, and r is the distance from the particle to the point where you want to calculate the field.

3. Can the field from a charge be negative?

Yes, the field from a charge can be negative. This indicates that the force exerted by the charged particle is in the opposite direction of the field. A negative field can also represent a repulsive force between two particles with the same charge.

4. How does the field change as the distance from the charge increases?

The field from a charge decreases as the distance from the charge increases. This is because the force exerted by a charged particle is inversely proportional to the square of the distance between the particles. As the distance increases, the force decreases, and therefore the field decreases.

5. Can the field from multiple charges be calculated using the same formula as for a single charge?

Yes, the field from multiple charges can be calculated using the same formula as for a single charge. However, you must take into account the contribution of each individual charge and add them together to find the total field at a given point. This is known as the principle of superposition.

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