Meet the Diode
One electronic device which we'll use in many circuits is the diode. A diode has a special advantage over other electronic parts which we'll see in this Project.
Wire this Project as shown in the first schematic. When you press the Key, LED will light. That means that current is flowing through the diode.
Now reverse the wiring connections to the diode as shown in the second schematic. Press the Key and see what happens. Were you disappointed?
The LED didn't light up, did it?
Can you think of a reason why? (No fair peeking at the answer)
A diode only conducts in one direction. This means it can change AC into a pulsing DC by conducting only one of the directions in which AC flows.
Diodes can also be used to change radio signals into electrical energy you can hear with an Earphone, This is called rectification and we'll see how this works later in Radio Section.