Let’s take a look at the steps required to build a circuit that allows electricity to flow correctly.
In each of the projects that we build at MakeCrate, we start by connecting a wire to the 5V connection on our Arduino to our breadboard, and then connecting the ground connection on the Arduino to the breadboard.
Once our additional components are in place, like an LED, we’ve got a complete circuit that allows electricity to flow from the Arduino to the breadboard, through the LED, connect to ground, and flow back to the Arduino.
So, the question is, why does electricity need to flow in a loop?
The flow of electricity behaves like the flow of water in a lot of ways. If a tank of water has a hose on it that as a cap on one end, then the water will not move. However, if the hose has an open end and loops back into the tank, the water can flow repeatedly, similar to an electric circuit.
You still might ask, though, why the electricity has to go from power to ground.
Think of the same tank, except this time, the hose loops back to below the original water line. Because the pressure on the water is the same at the hose beginning and end, the water can’t flow through the hose. If, however, the hose is moved above the water line, then there is water pressure at the beginning of the hose, but not the end, and the water can flow through the hose.
In a circuit, there is a voltage difference between power and ground that is similar to this difference in pressure at the beginning and end of the hose. This voltage difference between power and ground allows for electricity to flow freely through a circuit.