## Illustration 26.2: A Capacitor Connected to a Battery

voltage difference between the plates, ΔV = V

The animation represents a parallel-plate capacitor connected to a battery that is not shown. The red and blue circles on the plates represent the charge build up on the plates (position is given in meters, electric field strength is given in newtons/coulomb, and electric potential is given in volts). The plates are connected to a battery that maintains a constant potential difference between the plates. Restart.

How do the amount of accumulated charge and the magnitude of the electric field between the plates depend on the separation distance between the plates? Make a prediction and then test it by dragging the bottom (red) plate closer and farther from the top plate. (You must drag in the center of the plate.)

Notice that the battery maintains the electric potential difference between the plates. If we ignore the fringing effects of the electric field near the edges of the capacitor plates, the electric field is constant between the plates (from Gauss's law). Given this, the electric potential difference between the plates is related to the electric field by ΔV = -Ed, where d is the distance between the plates. Because of this relationship, a larger separation between the plates, for the same electric potential difference, means a smaller electric field between the plates.

How do the amount of accumulated charge and the magnitude of the electric field between the plates depend on the voltage difference between the plates? Make a prediction and then test it by changing the voltage difference. As stated above, the larger the potential difference, for the same separation between the plates, the larger the electric field, and therefore the larger the charge accumulation on the plates.

Illustration authored by Melissa Dancy and Mario Belloni.

Physlets were developed at Davidson College and converted from Java to JavaScript using the SwingJS system developed at St. Olaf College.

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