We will now discuss the simplest non-linear circuit component and it's water analogous equivalence: the one-way valve.

A one-way valve allows water to flow in one direction but not the other, as is shown in Figure 1.

Figure 1. A one-way value.

If I can come up with an interesting example, I will do so. The most useful examples are with alternating currents: currents which cycle between moving in one direction and then the other.

Light-emitting Diodes

For anyone desperate enough to want to find an analogy to a light-emitting diode (LED), consider the fountain-emitting one-way value shown in Figure 2.

Figure 2. A fountain-emitting one-way value.