We don’t consume electricity; we use energy; transforming it into different forms to make our world brighter, warmer (or cooler) and make work easier. We strive to conserve and efficiently use energy, but in the end, we really only change energy from one form to another. Energy never goes away; it just finds another job to do.
If electricity is only the transportation system for the energy we use, then what is electricity and how does it work?
Although the Money Pit is one of my favorite movies, here is an example of how electricity does NOT behave.
In the simplest of terms, electrical current is the excitement and flow of electrons. To understand what that means, we need to start with the most basic building block of all matter: the atom. All matter is made from a combination of atoms (either of one kind or multiple). Any substance that cannot be separated into a simpler substance by chemical means is considered an element. All known elements are cataloged within the ‘Periodic Table of Elements’, a table that has stressed out generations of high school chemistry students. The periodic table of elements describes the individual atomic characteristics of each element, and knowing those characteristics gives us more insight into how they all behave with each other. It’s not unlike knowing the personality types of your friends and co-workers.
Each atom is composed of three basic particles: the electron, proton and neutron. Protons and Neutrons are located in the atom’s nucleus, with the electrons orbiting around in a series of concentric “shells”. Science has uncovered even smaller particles that make up and hold together each atom’s structure, but for our purposes it is the negatively charged electrons (or their absence) that hold the secrets of electricity.
Early scientists such as a Frenchman by the name of Charles Dufay realized that certain materials became attracted to certain objects, but were repelled by others. The forces of attraction and repulsion are described as either a positive or negative charge. As neutrons have no charge, each atom’s nucleus has a net positive charge. As Paula Abdul’s 1988 hit described, “We come together, cuz opposites attract”. Objects with similar charges are repelled from each other, and those with opposite charges are attracted to each other.
At this point, I know that many readers are beginning to have flashbacks to early childhood science class and are wondering, “Where is he going with this? It’s about as exciting as watching paint dry.”
Excitement is exactly what electricity is all about. The outer shell (known as valance electrons) of each atom contains between one and eight electrons. Each atom seeks stability by filling up its outer shell with all eight; a nice calm retirement of sorts. Some atoms like the noble gases Argon and Xenon start out with their outer shells full; they’re calm, unexciting and don’t over-react. Other elements such as gold, silver and copper have only one electron in their outer shell and are more than willing to dance the night away in an attempt to lose that electron and settle down into a more stable existence (a very unlikely outcome given their propensity to getting over-excited). The following animation shows a copper atom, with only one electron in its outer shell. The nucleus, comprised of 39 neutrons and 39 protons is shown as a single sphere at the center (To be honest, I didn’t feel like modeling all 78 spheres in the nucleus; my obsessive nature does have its limits).
At the risk of perpetuating stereotypes, we can group elements and materials by how they behave when excited. In terms of electricity, elements and materials (combinations of elements) can be put into three groups:
Conductors, Insulators and Semi-conductors.
Elements with 3 or less electrons in their outer shells are generally conductors (although the exact number of electrons does not always determine which elements are the best conductors). Because they have lots of empty room in that outer orbit, they are less stable and more likely to lose their remaining electrons when bumped around (The bump theory is a commonly held explanation for how electrons are passed from one atom to another). Insulating materials such as wood, glass and rubber are combinations of elements that fill their outer shells by sharing their electrons with other elements. These materials are composed of elements such as Carbon, Oxygen, Nitrogen and Hydrogen. Alone these elements are not very stable, but combined they have found comfort and stability. Selective elements such as Silicon and Germanium are termed semi-conductors, and have 4 electrons in their outer shell. With a little encouragement these elements can be persuaded to lose an electron or two and become negatively charged. These materials have become indispensable in the development of solid-state circuitry and computers in general.
That bumping around of electrons in a conductor is precisely where the transfer of energy via electricity happens. Like billiard balls on a pool table, when the energy is introduced at one end (the player hitting the cue ball), energy is transferred from one ball to the next. Not all energy is passed from one ball to the next however. In billiards, you’d hear the sound of balls hitting, and if measured, you could see the heat generated by the instantaneous collision. With electrons in a conductor, that energy release may be heat, light and almost always a magnetic field.
Magnets? I thought we were discussing electricity?
Everyone has played with magnets as a kid (or adult). Those of us old enough to remember iron filing and magnet toys such as “Wooly Willy”, have seen what a magnetic field actually looks like. The following image shows a magnet with a negative and positive end (or “pole”) often termed a North and South pole. The iron filings align with the resultant magnetic lines of force (or ‘flux’). No we are not going to enter into a discussion of whether Santa Claus or penguins reside on either pole (maybe in a later post).
Magnetic fields, created by electrons flowing through a conductive material, are precisely what enables a generator or alternator to initiate the flow of electricity, and appliances such as motors to use that flow of electromagnetic energy to create mechanical movement.
This whole discussion can seem very theoretical, given that we can only see the results of what magnetics and electricity can do. So how do we measure that flow of energy across a conductor?
Before we talk about measuring electricity, it’s important to know why it flows at all. Electromagnetic energy will not flow through anything unless it has somewhere to go. OK, time for a few metaphors:
Everyone is familiar with water pipes in their house, or at least knows that water comes from somewhere when the faucet is turned on. Why doesn’t water flow continuously from the kitchen faucet? It doesn’t flow all the time, because without an open outlet (someone using that water), it will just sit nice and quiet in the pipe. Open a faucet, and the water begins to flow. Break a pipe or create a leak, and water will flow to places you don’t want it to. Electricity is very similar. Without a load, or something to use that energy, there is no need for the electrons to bump into each other and pass along their energy. Unlike the water in our pipes however, electricity wants to flow from a positively charged source to negatively charged one (this is according to popular theory, but let’s leave theory out of this for the moment as it gives me a headache). More often than not, that flow may be from a positive terminal of battery to the negative one, or a positive source to the earth itself (such as in a building’s electrical system). Without a complete “circuit” to follow, the electrons will have nowhere to go, and the flow of electricity will stop. If you provide a complete path for the electricity to follow, then it will happily oblige. There is a reason that they refer to the Formula One race car events as a circuit. If the road was open on both ends and didn’t connect, it would be a very short race. Yes, I’m aware that would be considered drag racing; metaphors have their limits.
Measuring the energy carried by electricity
Before I lose anyone, let’s talk about volts, amps and watts. In my next post we’ll talk about AC/DC, and by that I’m referring to Alternating and Direct Current, not the 80’s band from Australia. I’m sure everyone has heard the phrase, “It’s not the voltage you have to worry about; it’s the amps”. While partially true; why? It has to do with force and potential energy.
If electricity is the flow of electrons, then measuring energy carried by electricity must involve electrons right? Well, unless you have an incredibly powerful microscope, and someone who is really fast at counting, we’re going to need a standard to measure against for counting electrons. Here we learn about Charles-Augustin de Coulomb, a French physicist whom the standard imperial measurement of charge was named after (his story would be another post). One coulomb is equivalent to the charge of 6.242 X 1018 electrons. That’s a lot of electrons. In obnoxiously large numeric terms, that’s six quintrillion, two hundred and forty-two quadrillion electrons. That should be easy enough to put into an Excel spreadsheet, right? Well, instead of counting every electron over a period of time, how about we just divide the total number of electrons by a nice big number like a coulomb? Well it so happens that the volume of one coulomb per second is referred to as an ampere. Whoa! Amps are actually related to something physical?! Don’t get too excited, we’re still talking about theoretically numbers and some basic assumptions, but at least we have somewhere to start.
So if one ampere (normally referred to as an Amp), is a volume of electrons over time, then we should be able to measure the energy those electrons are moving with them right? Not so fast. Volume (or size) is one side of the equation, but we’re missing the other half. We need a push. We need that potential energy to work with.
Caution: Dangerous metaphors ahead.
What is potential energy? If your house was on fire, and you asked for a water hose; I’m sure you’d be rather upset if someone walked up with a garden hose connected to a hand pump. You’d prefer a fire hose connected to a rather large fire truck I’m sure. Why? The difference is in potential energy. Only so much water can flow through a garden hose. Given a bigger and stronger hose, you could push more water through it. Water is normally measured in volume over time; commonly gallons per minute. A garden hose can easily provide 10 gallons per minute, but so can a fire hose. The fire hose however has the potential to provide much, much more water if it is needed (which it usually is). Here’s another example: Let’s say you are sitting quietly at the base of ten-foot cliff, and a rock is perched very precariously above you. It’s not moving, but given a bit of a push, it could fall at any time. If that rock weighed a few grams, the potential for harm to your pretty head is minimal. If that rock weighed 10,000 lbs., then the potential for harm would be rather substantial. Unless it’s actually falling, both rocks are harmless. The 5-ton rock however has a much larger potential energy (it COULD exert a much bigger force).
Since electricity transmits energy, we need to know the volume of energy over time, but we also need to know the level of force with which it is delivered. In terms of water in a pipe, this potential energy is referred to as pressure (in pounds per square inch, or PSI). In the flow of electrons, this potential energy or pressure is called voltage. One Volt is the potential energy it would take to drive one amp of current against a given load (we’ll talk about loads in the next post).
Now we’ve brought energy and force into the equation. Flowing electrons mean nothing if they bump off a conductor one at a time, but if they flow in great numbers (along with their accompanying magnetic fields) with a large amount of force, then now we have energy we can use. With both volume and force, we can move almost anything.
So how do we measure the power or work that electricity provides? Enter the “Watt”. One watt is equal to one volt of potential energy times one ampere of flow. The watt is a measure of the real power that pushes, heats or illuminates. For comparisons, this would be similar to horsepower (735.5 watts), or foot-pounds of force per second (1.355 watts).
In electrical terms, the watt, is proportionately equal to the volts (the potential energy) times the amps (the volume of flow). 1 Watt = 1 Volt x 1 Amp. I know. Some of you just went… uh, duh, but the majority of people just had that little 13 watt LED light bulb (equivalent to a 60 watt incandescent bulb) go off in their head and said, “Oohhhh, I get it.”. You’re welcome.
So let’s stop there for the moment, because unless you’re an electrical engineer or a geek like me, you may need a week to recover from reading this post.
Next time we’ll talk about Direct Current, Alternating Current, Single-Phase Power, Three-Phase Power, generators and transformers. I know, you’ll have a tough time waiting, but it should be worth it.
In the meantime, here is your moment of Zen (Yes, I’m a fan of the Daily Show on Comedy Central):
I promise not to beg, but I would really welcome any comments; both good and bad (but constructive). The more feedback I get; the better my posts can be. Thanks!!
The Money Pit, Copyright NBC Universal, 1986
A Christmas Story, Copyright Warner Bros. Home Entertainment, 1983
Magnet and Periodic Table images are public domain and are available on https://commons.wikimedia.org