Special Geometries for Electrostatics
There are two situations involving electric fields that are particularly nice because they can be described
with some relatively easy formulas. Let’s take a look:
Parallel Plates
If you take two metal plates, charge one positive and one negative, and then put them parallel to each
other, you create a uniform electric field in the middle, as shown in Figure 18.3 :
Figure 18.3 Electric field between charged, parallel plates.The electric field between the plates has a magnitude of
V is the voltage difference between the plates, and d is the distance between the plates. Remember, this
equation only works for parallel plates.
Charged parallel plates can be used to make a capacitor , which is a charge-storage device. When a
capacitor is made from charged parallel plates, it is called, logically enough, a “parallel-plate capacitor.”
A schematic of this type of capacitor is shown in Figure 18.4 .