Electric Field: Homework Solutions

AI Thread Summary
The discussion revolves around calculating the electric field above two large non-conducting sheets with identical positive charge distributions. The user initially believes that the electric field is zero due to the cancellation of fields from both sheets. However, the correct approach involves applying the principle of superposition, where each sheet contributes positively to the electric field above them. The correct value of the electric field is given as σ/ε0, indicating that the fields do not cancel but rather add together. Clarification is needed on the contributions of each sheet to understand why the initial conclusion of zero electric field is incorrect.
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Homework Statement



see below.

Homework Equations


The Attempt at a Solution

 
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See the attachment for the visual, but ignore the negative charges. They aren't supposed to be there.

The image is of two large non-conducting sheets with identical distributions of positive charge. What is the value of the electric field above the sheets? sigma is the symbol for the identical distribution of positive charge.

I know the answer: \sigma/epsilon\epsilon<sub>0</sub>

I know that you need to add to use the principle of superposition.

However I still don't get the answer. The top sheet adds \sigma/2epsilon\epsilon<sub>0</sub> upwards. The downwards from the top sheet is canceled out by the upwards (electric field) from the bottom sheet. The bottom sheet has an electric field that also points in the negative y direction but with the same magnitude. So everything cancels out. So the electric field is zero.

This is wrong. However, I still do not see why and why the right answer is right.
 

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