Electricity is Motion

  How Much? How Fast?

  What Capacity Means To Me

  Veins and Arteries

  More to come!

1. Electricity is Motion

These pages are primarily about home wiring, about your lamps and your appliances and that metal box with circuit breakers in the basement (or the back of a closet), and the mysterious things going on behind your outlets and switches and inside your walls.

But before we can talk about any of that, it's pretty important that you understand not just how electricity works, but how it performs work - why it is a source of energy and how that energy behaves.

None of this is rocket science. There is only one formula anywhere in these pages and it's a very easy one. Trust me on this: Electricity is not hard to understand. It's not even particularly hard to work with, at least not as far as minor home jobs (assuming one takes very careful precautions - but we'll come to that in due time).

But sometimes the basic concept of electricity being something that flows through a medium is a little tricky to get, so let's start by considering something that actually works pretty well as an analogy to electric current - at least up to a point.

Water.

You may never have actually seen water turning a turbine or a mill wheel, but the principle is easy enough to understand: The motion of water - travelling through a pipe or down a stream - is used to move other objects, and that motion is a form of work. Water flows past and hits the surfaces of a turbine or water wheel, turning the wheel; this rotary motion is then used to generate electricity or grind wheat or what-have-you. Again: It is the motion that does the work.

Electricity is also motion of a substance through a medium. The substance is electrons, and the medium (in our home-wiring universe) is usually copper wire. I realize it isn't intuitive to think of something "flowing" through a solid, but electrons can do it.

Actually - while it's not worth delving too deeply into what happens at the atomic level - electric current isn't so much a flow of constantly moving electrons as a chain reaction. You know those desk toys where ball bearings thump into one another ("Newton's Cradle")?

Imagine that you had a much longer chain of those. That's how electrons flow (greatly oversimplified, but good enough for us). One nudges the next one, and pushes that into the next one, and that pushes the next one, and so on.

Or, as one of my science textbooks once had it, imagine you're pushing marbles into one end of a tube already filled with marbles. Each time you push one into one end, it displaces the whole set a little, and one pops out the far end. Push in marbles fast enough and you have a constant flow of marbles popping out the far end.

While it may make the atomic-scientist types cringe, for our purposes, we can think of electricity doing work via motion exactly the same way water does. Of course, it's always a little more complicated than that. For example, an electric motor actually works by quickly making and breaking magnetic fields to translate electromagnetism into rotary motion. (See these pages or search for "paper clip electric motor." It's a standard home science project.) But it won't hurt anything if we think of electricity turning an electric motor by thumping against it the way water thumps a turbine.

One difference between the flow of electricity and the flow of water is that the latter doesn't build up much heat. All motion generates heat - it's the by-product of all work - but water is very good at carrying heat away and dispersing it (which is why we use it to cool things down), so we don't have a problem with our water pipes overheating. Wire is not so good at dispersing heat, and usually has the disadvantage of melting and catching fire if you get it too hot. Later, we will discuss the many safeguards in your home wiring to prevent excessive heat buildup.

Some applications of electricity use this to advantage - by heating a wire or other element, made of something that won't melt at the maximum temperature it reaches, until that by-product heat is sufficient to do something useful, such as dry your hair or toast bread or light a room (the filament in an incandescent light bulb is made to get so hot that it glows).

Unfortunately, direct generation of heat is an extremely inefficient (read: expensive) use of electricity, which is why your house is almost certainly heated by burning some sort of fuel directly on the premises, and not by electrical power. Any large appliances which use direct electrical heat (non-gas clothes dryer, dishwasher which has its own heating elements) will be the biggest power hogs in their class in your house, just as your toaster and hair dryer are the biggest hogs among the small appliances. Incandescent light bulbs consume a relatively small amount of power, but even so, it's more efficient to produce light by using electricity to excite gas molecules (fluorescent tubes, halogen lamps) than by direct heat, which is why the ecological types would like us to change to fluorescents and make our houses look like morgues.

The third common way electricity is used in your home - after turning a motor or deliberately heating some object - is based on the fact that if you coil wire around a bar/cylinder of certain substances and send electricity through that coil, you have created a magnet that only operates while it has electrical power - a magnet that can be turned on and off, unlike magnets made from naturally magnetic substances.

Furthermore, if you don't secure the bar of substance in the middle of the coil - say, if you put a nail inside a paper tube, it will move when you turn on the current through the coil - if it's partially inserted, the magnetism will try to pull it all the way into the coil. The amount it moves depends mostly on how much power is pushed through the coil. This means you can use it to generate different sounds (by vibrating a paper cone) by varying the power - this is how speakers work. Or you can use the motion of the bar as a striker to physically thump something. This is how some non-electronic doorbells work (see the last couple of illustrations in the link above).

It is also how you use electrical power in one place to switch on a different set of electrical circuits in another place (by using that motion to close a physical switch). The starter solenoid in your car works like this.

All of this, though, stems from the basic idea of motion through a medium. Electricity is about something moving.

Where does this motion originate from? From other kinds of motion.

Electricity that is generated from wind power depends on flow of air; hydroelectric power from flow of water. Those flows are generated by natural forces (movements of hot/cold air masses generate wind; gravity and/or underground pressure produce water motion). Combustion plants (oil, coal, gas, and for our purposes, nuclear) work by heating water (or, rarely, some other substance) until it is gaseous; gases flow naturally from high-pressure and/or high-temperature areas to low-pressure or low-temperature ones, and that motion is used to generate electricity.

It is okay to think of electricity as a transfer method for changing one kind of not-easily-stored motion into another kind which can be stored and transmitted long distances; when the electricity gets to its destination, the work it does often means translating that motion back into physical motion again.