"A zener diode is a special kind of diode that acts like a normal diode when it is forward-biased, but also allows current to flow when it is reverse-biased if the voltage difference between the anode and the cathode exceeds a characteristic breakdown voltage. In the water analogy, a diode is like a one-way gate with a spring -- water pressure in one direction will stretch the spring and open the gate, while pressure in the other direction will close the gate. A zener diode is like a gate with a weak spring holding it closed in the forward direction and a stronger spring holding it closed in the reverse direction."
METAMIA is a free database of analogy and metaphor. Anyone can contribute or search. The subject matter can be anything. Science is popular, but poetry is encouraged. The goal is to integrate our fluid muses with the stark literalism of a relational database. Metamia is like a girdle for your muses, a cognitive girdle.