Calculating E-field Through Layers w/ Diff. Permittivities & Conductivities

In summary, the conversation discusses the changes in total electric field as it passes through layers with different electrical permittivities and conductivities. The external field is assumed to be uniform and the goal is to find the profile of the total normal component of the E-field along a specific line. The conversation also mentions the presence of a secondary electric field due to surface charge accumulation at the interfaces between layers, and the question of whether this field needs to be considered in the calculations. The conversation also mentions the steady state of the system and the behavior of the electric field in different scenarios. Reference to Griffiths' work is suggested as a helpful resource.
  • #1
ThomasAnderson
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I'm trying to understand how the total electric field changes as it passes through layers with different electrical permittivities and conductivities (as shown in the linked figure). The rectangular prism layers are assumed to be very thin. The conductivities ##\sigma## and relative permittivities ##\epsilon_r## for the 5 layers as well as the surrounding medium are labeled. The external field ##E_0## is uniform. I'm hoping to find the profile of the total normal component of the E-field along the line A-A'.

I assumed that the profile would have a stepped pattern as shown in the right panel. For example, the electric field normal component inside layer 2 would be ##E_{n,2}=E_0/\epsilon_{r,2}##, and similarly for the other layers.

However, I also recall learning that there is a surface charge accumulation that occurs at the interfaces between each layer, due to the difference in conductivities. If I understand correctly, these surface charges create a secondary electric field. I don't know if I need to find this secondary field, and I'm not sure how I would calculate it. I would appreciate some guidance on this problem!

https://i.stack.imgur.com/UHQ7L.png
 
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  • #2
Do things vary with time or are you interested in steady state (after system settles)?
 
  • #3
hutchphd said:
Do things vary with time or are you interested in steady state (after system settles)?

I was interested in the steady state
 
  • #4
For any finite conductivities, the charge will migrate to the opposing surfaces and the field inside will be zero (ignoring edge effects). Not very interesting?

For all conductivities zero the Displacemant field D will be E0 and the local E will be εD rE0 in each slab. I think Griffiths does a nice job on this general subject.
 
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What is the formula for calculating the electric field through layers with different permittivities and conductivities?

The formula for calculating the electric field through layers with different permittivities and conductivities is: E = E0 * e-kx, where E0 is the initial electric field, k is the wave number, and x is the distance through the layers.

What is the significance of permittivity and conductivity in calculating the electric field through layers?

Permittivity and conductivity are important factors in calculating the electric field through layers because they determine how easily an electric field can pass through a material. Higher permittivity means a stronger electric field, while higher conductivity means a weaker electric field.

How do you determine the direction of the electric field through layers with different permittivities and conductivities?

The direction of the electric field can be determined by the direction of the gradient of the electric potential. The electric field will always point in the direction of decreasing potential.

What is the relationship between permittivity, conductivity, and the speed of the electric field through layers?

The speed of the electric field through layers is directly proportional to the permittivity and inversely proportional to the conductivity. This means that a higher permittivity or lower conductivity will result in a faster propagation of the electric field through the layers.

How can you use the calculated electric field through layers to determine the behavior of charged particles?

The electric field can be used to determine the force exerted on a charged particle, which can then be used to predict the particle's motion. For example, if the electric field is directed towards a layer with higher permittivity, the charged particle will experience a force towards that layer. This can help in understanding the behavior of charged particles in different materials.

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