Gauss' law which formula to use

AI Thread Summary
The discussion focuses on determining the correct formula for calculating the electric field due to surface charge density, represented as E=a/2ε0 for a single charged sheet and E=a/ε0 when considering two sheets. The confusion arises from the application of Gauss's law and how the choice of Gaussian surface affects the resulting electric field calculations. It is noted that for a single non-conducting sheet, the electric field is halved when using a Gaussian surface that intersects the sheet. The participant seeks clarification on why the electric field appears to differ based on the Gaussian surface used, questioning the consistency of the results. Understanding the relationship between the surface charge density and the configuration of the Gaussian surface is essential for accurate calculations.
teknonjon
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Homework Statement



how do I know which equation to use for electric field? E=a/2e0 or E=a/e0 when a = surface charge density.

Homework Equations





The Attempt at a Solution

 
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first one is for single surface of a charged sheet ... when it is accompanied by another it changes to the second one (therefore it is twice of it)
 
I looked in my physics book and they use the formula E=a/2e0 when there is only one nonconducting sheet. The picture they show is a cylinder which is the Gaussian surface going through the sheet with both ends outside of the sheet. When they use the formula E=a/e0 half of the Gaussian surface is within the sheet so only one end of the cylinder is sticking ouside the sheet. I don't understand how making the changing the Gaussian surface like this would result in one answer for the electric field being only half the other. Shouldn't the electric field be the same no matter what you use for the Gaussian surface?

thank you for your reply earlier
 
What is the electric field within a conducting material?
 
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