Suppose this parallel plate capacitor is connected to a 9-volt battery. A volt is a measure of the electric potential difference. In short, this is the electric potential energy per charge—it’s a measure of how much energy a charge would gain by moving across that potential. So, this 9-volt battery will create a 9-volt change in potential across the plates.
But what would happen if you pushed one of the plates so that the distance between them decreases just a little bit? Well, since the capacitor is still connected to the 9-volt battery, then the potential would still need to be 9 volts. However, if the electric field stays the
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