Electromagnetism –revising with past exam papers

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Homework Help Overview

The discussion revolves around a problem related to electromagnetism, specifically focusing on a question from a past exam paper concerning the displacement field and free surface density in a dielectric material.

Discussion Character

  • Exploratory, Conceptual clarification

Approaches and Questions Raised

  • The original poster attempts to understand the relationship between the displacement field (D) and the electric field (E), questioning how to find the free surface density. There is a suggestion that the complexity of the question may relate to the marks allocated.

Discussion Status

Participants are engaging in clarifying the correct relationships between the variables involved. Some guidance has been offered regarding the use of Gauss's law and the correct expression for D, indicating a productive direction in the discussion.

Contextual Notes

The original poster expresses uncertainty about their answer due to the high mark value of the question, suggesting that there may be additional complexities or considerations that need to be addressed.

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Homework Statement


upload_2017-5-14_14-24-33.png

trying to do question C

Homework Equations


I know my answer to C cannot be right because it's worth six marks, any help or tips would be greatly appreciated. :)

The Attempt at a Solution


upload_2017-5-14_14-33-27.png
 
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Check to see if you have the correct relation between D and E.
 
thanks TSny you're right I have got that the wrong way round, I am more perplexed by question c though, how to find the free surface density, if I had the correct value for the displacement field of the dielectric would my answer for c be right? I'm assuming it wouldn't as it's awarding 6 marks, so must be more complex.
 
I think your answer for (c) would be correct once you use the correct expression for D in terms of E. Maybe they feel that (c) requires more conceptual thought in using Gauss's law for D.
 
ok great thanks TSny
 

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