Area of a Parallel Plate capacitor. Pi*r^2?

AI Thread Summary
The discussion revolves around the calculation of the area for a parallel plate capacitor, specifically addressing the use of the formula pi*r^2 for a circular electrode. The initial confusion arises from the assumption that the area should be based on the length of one electrode multiplied by the distance between electrodes. It is clarified that the relevant area is indeed that of one electrode, where the charge resides. This understanding aligns with the formula for electric field calculation, E=sigma/epsilon0. The conversation concludes with a consensus on the correct interpretation of the area in this context.
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Hi,

I was just going through a question in my Physics textbook today. In calculating the electric field (E=sigma/epsilon0) ... sigma = charge density = q/Area ... they have used the area as pi*r^2, I can't understand why this was done? shouldn't the area of the parallel plate capacitor be length of one electrode * distance between electrodes?

Hope I'm making sense!
 
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No, the area that we use here is the area of one of the electrodes (circular in this case, apparently). The charge resides on the electrodes, not in the space between them.
 
Hmm, makes sense. Thanks mate!
 
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