Saturday, September 28, 2013

Physics - Parallel Plate Capacitor

This will be an introduction into the basic physics of a capacitor. A parallel plate capacitor is when we have two electrodes placed a distance d apart. One is charged Q and one is charged -Q which means that the capacitor doesn't have any net charge. Therefore with the exception of a small fringe field at the edges of the the capacitor we don't have a field when we view a capacitor from afar we don't see a net electric field.

The electric field within the electric field is due to both plates. The field form the positive plate points away form the plate in this case to the right, and the electric field from the negative plate points towards the plate which is also the right. Therefore

E = Q/ε0A

This is an approximation for infinitely sized parallel plate capacitors but this is actually a good approximation for real world capacitors assuming d is much smaller than the size of the electrodes.

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