Why does electricity only flow through the copper on a circuit board? Simple! Copper, like most metals, is a conductor of electricity. That means that electricity can easily flow through it, as opposed to an insulator which is a material that electricity does not easily flow through, like rubber or plastic.
So why does electricity flow easily through conductors? Well, that is a little more complicated to explain. Basically, think of electricity as energy that flows through electrons. Some of the outermost electrons of metal atoms aren’t strongly attracted to the nucleus. This creates a sort of “cloud” of electrons that easily move around, thereby easily allowing them to transfer energy. Let’s build a conductivity tester so you can test substances to see how conductive they are!
What You Need:
3 Alligator Clip Wires
A 12VDC Buzzer
A 9V Battery
Things to Test
What to Do:
Connect one wire to the negative (-) terminal of the battery.
Connect the other end of the wire to the black wire on the buzzer, making sure the metal on the clip is grabbing the exposed metal of the wire.
Connect a second wire to the positive (+) terminal of the battery.
Connect a third wire to the red wire on the buzzer, making sure the metal on the clip is grabbing the exposed metal of the wire.
To test the circuit, touch the two empty alligator clips together.
Place a material between the two clips to test them. Or, you can immerse the two ends into liquids to see how conductive liquids are.
In order for electricity to flow through a circuit, the circuit must be a complete loop – from the battery, to a device, then back to the battery, through a conducive material. This is called a “closed circuit.” The two open alligator clips act as a type of switch, controlling when the circuit is open or closed. When a conductive material is placed between the two clips, the circuit is complete and electricity can flow.
By the way, it is important to connect the buzzer as I described above. It is like a one-way street – electricity can only flow one direction through it. Connect it the other way and it won’t work! There are several devices like this, just like there are some that can electricity flow through either direction (like a light bulb).