Explain how a diode is like a one way street

The diode is like a one-way street because it allows current to flow to only one direction in the circuit.

In fact, a diode consists of a p-n junction, with a n-type region with excess of electrons and a p-type region with excess of holes. Both ends are connected to two terminals of a battery, so a voltage difference can be applied across the junction.

When no voltage is applied, electrons from the n-region combine with the holes from the p-region in the area near the junction, creating the so-called depleting region, which acts as an insulating area.

To get rid of this depleting area, the n-type region must be connected to the negative terminal of the battery while the p-type region to the positive terminal of the battery. This way, electrons from the n-region are repelled from the negative terminal and start to flow towards the positive terminal (and the holes do the same in the opposite direction), creating a net current flowing through the depletion region. Instead, when the n-type region is connected to the positive terminal of the battery, the electrons are attracted by that terminal, so they do not flow through the depletion region (and same for the holes in the p-region) and so there is no net current across the junction. Therefore, current in a diode flows only in one direction.