This is the first in a series of posts covering technology basics.

We’re all familiar with electricity, as it comes out of a socket or a battery, but what is it, really? Electricity is basically charged particles (electrons) in motion, usually through a wire or other conductor. Remember playing with magnets in kindergarten? Opposites attract (positive to negative), and like charges repel one another. The labels of “positive” and “negative” and directionality associated with electricity date from before the discovery of electrons and are, in a significant sense, backwards. Electrons have a charge that had already been labeled as “negative,” so what we think of as electric current flowing from positive to negative is really a “negative current” of electrons flowing from negative to positive. A positive charge is really a deficit of electrons, and so there are “holes” that electrons fill. You can think of this as being like one of those childhood puzzles made up of tiles in a frame with one missing tile, so that you can slide the tiles around until they’re arranged to form the appropriate picture. What’s actually moving are the tiles, with a new hole formed by the movement of each tile, but you can also think of it as one hole moving from location to location.

There are two words associated with electricity that we’ve all heard. They are “voltage” and “current.” What do they mean? Well, think for a moment of water in a pipe instead of electricity in a wire. Voltage is the equivalent of pressure, and current is equivalent to volume. These two values are independent. Each can be greater or lesser without regard to the other. You can have high volume and high pressure, as in a fire hose. You can have high pressure and low volume, as in a squirt gun. You can have low pressure and high volume, as in throwing a bucket full of water. And you can have low pressure and low volume, as in an eye dropper. With electricity, you can have power lines (high voltage and high current), TV tubes (high voltage and low current), stereo speakers (low voltage and high current), and electronic devices (low voltage and low current).

You’ve no doubt also heard of “AC” and “DC,” or Alternating Current and Direct Current. Your wall socket (if you’re in North America) is 120 volts, and the electric current reverses direction back and forth sixty times each second.  That’s AC. A battery, whether in your car or your calculator, is DC. The electric current always flows in the same direction.