Gauss's Law - field of infinite plane sheet

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Homework Help Overview

The discussion revolves around applying Gauss's Law to determine the electric field produced by an infinite plane sheet with a given surface charge density, σ0. Participants are exploring the implications of the solution provided and the reasoning behind specific components of the formula.

Discussion Character

  • Conceptual clarification, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants are questioning the presence of the factor of '2' in the solution, with some suggesting it relates to the two sides of the sheet. There is also inquiry into the choice of Gaussian surface, with a cylinder being proposed as a possibility.

Discussion Status

The discussion is active, with participants offering insights into the nature of the electric field and the flux through the Gaussian surface. There is a focus on understanding the contributions to the total flux and the reasoning behind the calculations, though no consensus has been reached on all aspects.

Contextual Notes

Participants are working from a solution that lacks detailed derivation, which has led to questions about the assumptions made regarding the Gaussian surface and the electric field's behavior around the sheet.

ZedCar
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Homework Statement



Use Gauss's Law to calculate the field of an infinite plane sheet of surface charge density σ0.


Homework Equations





The Attempt at a Solution




The solution is, where A=area:

2EA=(σ/ ϵ0)A

E=σ/2ϵ0


Why is there a '2' in the solution? I know it's something to do with twice the electric field. Is it because there are two sides to the sheet surface?

Thank you.
 
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The solution is, where A=area:

2EA=(σ/ ϵ0)A

E=σ/2ϵ0

What gaussian surface did you use to get this?
 
ap123 said:
What gaussian surface did you use to get this?

Possibly a cylinder?

I'm not 100% sure, as I just have the solution as shown above, and no other 'working out'.
 
ZedCar said:
Possibly a cylinder?

I'm not 100% sure, as I just have the solution as shown above, and no other 'working out'.

Sounds a good choice.
What will the flux be through the cylinder?
 
ap123 said:
Sounds a good choice.
What will the flux be through the cylinder?

Not through it in one direction.

It's normal to the surface of the sheet.

As the sheet has two surfaces, the E-field is in both the two normal directions to the sheet.
 
ZedCar said:
Not through it in one direction.

It's normal to the surface of the sheet.

As the sheet has two surfaces, the E-field is in both the two normal directions to the sheet.

Since the field is normal to the sheet surface, the flux through the sides of the cylinder is zero - so that only leaves the 2 cylinder ends. What's the total flux through these?
Hint : you've already got the answer :)
 
ap123 said:
Since the field is normal to the sheet surface, the flux through the sides of the cylinder is zero - so that only leaves the 2 cylinder ends. What's the total flux through these?
Hint : you've already got the answer :)

2EA=(σ/ ϵ0)A

Where A, area, is the area of one cylinder end. i.e. ∏r^2
 
Yes, so the 2 comes from the fact that the flux through each cylinder end is EA
 
Thanks very much ap123..!
 

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