What is Electricity?
Electricity is everywhere: it powers our homes, our transportation, and our entertainment. Electricity is the reason that you can read this article right now!
But what is electricity?
The importance of understanding the basics of electricity (what it is and how it works) cannot be understated. Without understanding electricity, you could not design all of the electrical marvels of technology we have today (from the modern power grid to a cell phone). Even more importantly, you wouldn't be able to protect yourself from electricity. So in order to understand how electricity works, I'm going to first talk about the two key components that make up electricity: voltage and electric current.
Voltage
Voltage is the difference in electric potential energy between two points. If you pick a single point on an electrical circuit and ask “How much voltage is here?” the person trying to answer you will probably say “compared to what?” Think of it kind of like distance. If you're standing at one end of a room and I ask you “How much distance is there?” you're going to be confused. If I ask you “How much distance is there between you and the other side of the room?” you're going to tell me that there's roughly 20 feet between you and the wall.
Voltage works the same way. If you look at two points in a circuit with stuff between them, you can use a multimeter to figure out the voltage.
Electric Current
Current, on the other hand, is harder to explain. Everything in the universe is made up of atoms: the building blocks of life. Atoms have three parts: protons, neutrons, and electrons. Protons and neutrons hang out together and form a sort of “core” of the atom, while electrons float around outside this core. In an electric circuit, one electron gets bumped off its atom and moves to a new atom. The new atom doesn't want too many electrons (it had enough before!) so it kicks off another electron. This happens over and over again millions of times in a circuit, (One amp means roughly 6.24*1018 electrons are going around the circuit every second!)
Electrons moving creates electric current, and electrons only move when there is an electric potential energy difference (voltage) between two points. The electrons are moving to try and bring balance to the system (bring the voltage between two points to zero).
Rho is resistivity, a physical constant that changes based on what material the electrons are travelling in. L is the distance the electrons have to travel, and A is the cross sectional area of the medium they're travelling in. Resistance depends on the mathematical equation shown above. So a really long, thin wire would have a much bigger resistance than a shorter, thicker wire.
Think of electricity like water in a pipe. It's easier to move water a short distance through a big pipe than it is to move it a long distance through a skinny pipe.
The Danger
This is where electric current gets very dangerous. Your skin is a great insulator, which means that it has a really high resistance. But the human body itself is a great conductor, which means it has a low resistance. Think about thunderstorms: why is it always safer to be away from the water? Especially salt water? Salt water is a great electric conductor. To electricity, the human body looks like a big bag of salt water: if you can get past the plastic (insulator), you can zip through the water (conductor) to the other side with ease.
When the current moves through your body, it can do a number of things. The heat from all those moving electrons can cause serious internal or external burns. Even worse, the electric current coming into you can interrupt the electric current that keeps your heart pumping!
So how can we keep ourselves safe?
People haven't been sitting on their haunches for the last 200 years since electricity was discovered. The most common ways of protecting people from electricity involve proper grounding and insulation design, appropriate personal protective equipment, and safe working practices. We've come up with things like equipotential zones and isolation transformers that greatly reduce the risk involved with working on or around electric equipment.
These are just a small sample of ways that we stay electrically safe today. What could you do to keep yourself and your designs electrically safe?
