What is Voltage?

There are a lot of terms associated with electricity. Different words refer to a current’s strength, the speed at which it travels, and the rate at which it’s consumed. Voltage is a sometimes-misunderstood term that means “electomotive force” or, more simply, electrical “pressure.” Voltage also is the difference in electrical potential between one end of a circuit and the other. In our electrical systems, voltage is measured against the earth, which is at zero potential. In other words, it all starts with the ground under your feet. Voltage gets the electrical ball rolling by giving a push to electric power from your utility’s generator to your house or business.
Long-distance power lines carry huge voltages, from around 155,000 to 765,000 volts. If you hooked your vacuum cleaner up to that kind of power, you’d melt its engine instantly—and possibly yourself as well. You previously read that transformers reduce the voltage before it enters your house. A few hundred thousand volts might sound like fun to your kids, but you should be grateful that you end up with a lot less voltage, thanks to transformers.

What is Grounding?

Now that you know what kind of current you have in your house (and everywhere else), let’s discuss another critical feature—grounding. Your entire electrical system, if it’s up to current code, is grounded for your protection. This literally means that one wire of your electrical system leads back into the earth itself, where it will carry any errant current that could otherwise shock or electrocute you. The earth ends up being a good electrical conductor and a convenient return path for electrons. In fact, the earth is used as a reference point for measuring the voltage in our electrical systems.
A ground wire can be attached to a ground rod that is deeply buried, or it can be a length of copper wire buried near your foundation’s footings. A second physical ground is usually your cold-water supply pipe near your service panel.
Modern house wiring is color-coded so you won’t confuse your hot, neutral, and
ground wires with one another. This coding is standard everywhere—there is no room
for artistic creativity here. The wire colors are …

• Black and red for hot wires
• White for neutral wires
• Bare (unsheathed) copper or green for ground wires

The black, red, white, and green colors refer to the plastic sheathing that contains the wires themselves. If you have an old two-wire system , you won’t have a ground wire. An old knob-and-tube system sheaths both the hot and neutral wires in black, which isn’t exactly user-friendly when you’re trying to distinguish one wire from another. It’s important to understand the difference between the grounding wire and the neutral wire.
The neutral white wire carries the electrical current back to the power source after it’s passed through a load (a ceiling light, a fan, a stereo, and so on).
That’s the nature of an alternating current. The grounding wire, on the other hand, protects the entire system. The neutral wire is more correctly referred to as a grounded conductor. The bare or copper wire is a grounding conductor.

What is AC/DC?

When Thomas Edison and his crew invented a reliable electric light bulb, he followed it up by developing the power systems to run it, rightfully envisioning a future world full of light bulbs. (We usually refer to these as “light bulbs,” but “lamps” actually is the correct term. Bulbs are for planting.) Edison employed direct current (DC), which now is used in battery-operated gadgets in which the current flows from the negative terminal of the battery to the positive terminal. A battery is basically a container of chemicals whose electrochemical reactions produce excess electrons. Our electrical systems use alternating current (AC), which was developed by Edison’s contemporary, George Westinghouse, after he bought up patents from Nikola Tesla and William Stanley. Once again, someone with business sense trumped the scientific minds possessing the money-making ideas. It took Edison, the lampmeister, a few years to go along with this AC business, but he eventually told Westinghouse’s son to let his dad know he was right.
A direct current just means that the electric current flows continuously in one direction and keeps going until it finds something to run such as a radio or a light bulb. An alternating current flows in one direction—say, to a receptacle—and then flows back in the opposite direction. You might be thinking, so what? When was the last time alternating current was discussed on late-night talk shows? Probably never. Alternating current, however, does have some useful, consumer-friendly features such as the following:

• Through a series of transformers, an AC can be increased or decreased in value. (The current can be made stronger or weaker.) This means that, instead of a zillion watts of power heading for your panel box, you’ll get a reduced amount that you actually can use.
• Alternating current is efficiently transported over long-distance power lines.
• It’s easy to convert from AC to DC, but it’s expensive to go from DC to AC.

Staying Current

Electricity doesn’t do us much good if a bunch of errant electrons constantly change orchestras from one conductor to another. We want our electrons to move in a reasonably orderly fashion so they can do our bidding when we turn on the lights. A flow of electricity is called a current, and it’s carried into our homes through wiring from local electric utility companies. New electrical systems have the following three wires coming into your house:
➤ Two black or “hot” wires that carry the current to your service panel
➤ One bare neutral wire for carrying the current back to the power source and to ground An electrical current has a couple of different options, depending on your application.

Going with the Flow

Think back to your high school physics classes and all those diagrams of atoms with electrons spinning around a nucleus. (They’re the drawings that looked like really small solar systems.) Basically, electrons spin around because the protons in the atom’s nucleus carry a positive charge (+) that repels the electrons’ negative charge (–). If enough of the electrons decide to move on, preferably in a more or less uniform stream, we end up with usable electricity.
Electricity comes in several flavors, but the two we’re most familiar with are …
➤ Static electricity, in which the electric charges are stationary.
➤ Dynamic electricity, in which the electric charges are moving in a current.
When you were younger, the main value of static electricity was using it to shock unsuspecting siblings and cousins after you had walked across a carpet. If you didn’t do this when you were a kid, you can always try it at your next holiday dinner. Cats also are good targets, but their revenge usually is a messier affair. Why does the shock occur? Because some electrons like to travel, and they aren’t the most stable subatomic particles. When you walk across a carpet (some are worse than others), you pick up some of these hitchhiking electrons while leaving some of your own positive charges. They have to go somewhere, and your sibling’s finger or a doorknob makes a dandy conductor. If you touch a door frame, nothing happens because wood is a good insulator. That is, it does not allow electrons to easily move through it.
Static electricity is simply an imbalance of positive and negative charges. When you get zapped, you’re just the accountant trying to balance these charges. One place you don’t want to balance these charges, by the way, is with your computer, so you can either …
➤ Touch your metal desk chair before turning on your computer to get rid of any pesky electrons that could affect your computer.
➤ Apply anti-static spray periodically to your carpet so it will have a more positive charge and be less likely to give up its electrons. Static electricity may be annoying, but dynamic electricity is another story altogether.

About Electricity

We use and depend on electricity every single day. All we usually know about it is that it’s buried inside our walls, it runs our lights and VCRs, and we’re billed for it every month or so. Terms such as kilowatt hours, amperage, volts, and current are Greek to most of us. This is probably appropriate because the Greeks first described static electricity about 2,500 years ago. It was discovered that amber would accumulate a negative charge of static electricity when rubbed with sheep’s wool. Not known for a great sense of comedy, this probably became quite the party trick at Greek get-togethers. The word “electricity” has its root in the term electrum, which is Latin for “amber.” Understanding electricity is like understanding cooking: Once you know a bit about sautéing, cooking temperatures, seasonings, and how to make a decent pie crust, you can muddle through meal preparation and come up with more-than-edible results. If you know how electricity is produced and can toss around some vocabulary words, such as alternating current and resistance, you’ll be more comfortable with your electrical work. A task makes more sense when you understand its inner workings. This section isn’t going to give you enough information to challenge a Ph.D. in electrical engineering to a trivia contest at your local Jeopardy theme bar. You will, however, develop a working knowledge of electricity basics and how they apply to your own electrical system

Confused About Fuses?

Every fully electrified house has either a fuse box or a main panel box with circuit breakers. This is the distribution center for the power coming into your house. Without them, you would have one whopping current running through your walls that would burn out just about any appliance you tried to run on it.
Fuses were used until approximately 1950, when circuit breakers became the standard installation for new construction. The fuses most of us are familiar with are the round, screw-in glass types with a visible alloy strip inside the glass. These are called plug fuses. Cartridge fuses, which have a cylindrical shape, are the other common type of fuse.
If the current running across a plug fuse’s alloy strip exceeds the amperage of the fuse, the strip will melt, thus stopping the flow of electricity. There is nothing inherently wrong with a system using fuses, but they are dated and inconvenient. If you don’t have any spares around when one “blows”—you should always replace a fuse with one of the same amperage—you’re out of luck. The other problem with plug fuses is that a fuse with an amperage setting of 15, 20, 25, or 30 can be installed as a replacement for a burnt-out fuse even if the original size should have been 15 amps. Even though it is physically possible to install the wrong fuse, doing so could overload a circuit and might even start a fire in your home. To prevent this, the installation of an “S” type adapter will limit the maximum fuse size to 20 amps.