Electricity can be observed in many natural phenomena. If you have ever witnessed lightning in a storm or been zapped by a static shock or rubbed your socks on the carpet to shock your unsuspecting younger brother, you have experienced electricity in the natural world. More than that, the signal transmitting the feeling of shock from your finger was electrical, and the neurons that interpreted the shock inside your brain was electrical. Electricity is all around us, but humans have only harnessed electricity and controlled it to accomplish tasks for less than 200 years. Today, when we think of electricity, we think of those ways in which we have harnessed it, from light bulbs to computers to electric vehicles.
So, what is it?
Electricity is the flow of electrical current from a point of high potential to a point of low potential. Current flows in an electrical conductor in the same way that water runs downhill (from a point of high potential energy to a point of low potential energy) or the way water moves through a pipe (from a point of high pressure to a point of low pressure). Electrical potential is called voltage, so in a circuit diagram, a high potential is shown as a positive voltage and low potential is shown as a value at or close to zero. Current is then said to flow from the point of highest positive voltage potential to the point of lowest voltage potential. Batteries are shown in circuit diagrams as having a positive and negative terminal and current is described as flowing from the positive terminal, through the circuit, and back to the negative terminal. This is called conventional current theory.
The shocking truth about conventional current theory
Conventional current theory is the opposite of how electrons actually flow! Benjamin Franklin defined conventional current theory based on his experiments with electricity in the mid-18th century. He properly identified that electrical current flows from one charged location (i.e., having an excess of “electric fluid”) to another location (i.e., having a less than normal amount of “electric fluid”). What he did not know at the time was that electrical current was carried by electrons, so the buildup of excess “electric fluid” was really a negative charge. The result is that conventional current theory, on which all circuit diagrams are still based today, is backwards!
But here’s the doubly shocking twist: it doesn’t matter. It turns out that all electrical diagrams, circuits, and math work out exactly right as long as you are consistent in referring to positive and negative terminals, and the direction of current flow. So today, because of more than 200 years of convention, and electrical engineering development with that convention, it is the acceptable standard to refer to current flow from positive to negative in an electrical circuit.