A circuit needs a power source
Makey Makey Classic works through opening and closing circuits, just like any other button. Instead of the circuit being closed underneath your keyboard, the circuit is closed through the conductive objects you connect with alligator clips like your hand or your lunch or some tinfoil.
One of the things we know about Circuits is that in order to create a circuit that works must be closed. On a computer the circuit is closed through buttons like buttons/letters/numbers on your keyboard or your mouse or space bar. Today lets take a look at how the Makey Makey is set up.
Lets review the things you need for a circuit.
the ability for the electron flow to flow back into the power source.
And finally a Switch. In a Makey Makey you are the switch.