CAUTION: The color codes for wires referred to in this article are for USA only - I haven't a clue as to what the wire color codes for house wiring are in any other countries. Consult your local electrician for information.
Electricity is pretty magic stuff. You can't see it, you can certainly feel it, it can do a world of good for you and it can kill you. You may have heard the old adage that it isn't the voltage that kills you - it's the current. That is true. But if the voltage is high enough, the current will flow! If that path happens to be across your heart, you will probably die. And if there isn't someone there to do CPR you will probably not be able to try an electrical repair again - ever!
So here is some information that will help you understand the fundamentals of electricity so that you can fix an electrical circuit or appliance without tempting the grim reaper.
First, electricity flows in a similar fashion to water. Electrical voltage is akin to pressure of water in a pipe or hose. It is really that simple. When you increase the pressure in a pipe, the water comes out faster. Oh, another analogy - resistance to electrical flow is akin to a restriction in a pipe or hose, so that even if you increase the pressure in a water supply system you can't make water flow very much if the resistance is infinite - like the faucet is turned off. There can be no water flowing if the faucet is closed; there can be no current flowing in a circuit if the wires are hanging in free space. Opening the faucet is like giving electricity a path (lower resistance than air) to flow through, like an electrical appliance or a light bulb, or your body.
Now on to some practical stuff. Let's talk about a car battery. If you ever accidently shorted out a car battery's terminal like you might do with jumper cables, you saw a spark that looked like Willie the Welder was working. Soooo, if a car battery can make that kind of spark it can probably kill you, right? Well, not really. Don't get me wrong here - if you apply the energy in a penlight battery to your brain you can do serious damage - even kill yourself. But if you were to grab the terminals of a car battery with your hands you wouldn't even feel it. If your hands were soaked in salt water for a while you might feel a tingle but not a very strong tingle. The resistance of your normally dry hands is sufficiently high enough to limit the current to a few microamps. See, the old adage is correct in one sense - no current, no dead!
But we aren't talking about car batteries here, we are talking about the scary wires that run through your house. Wires that can bite - can kill.
The first thing you need to know is that electricity needs a completed path in order for current to flow. So if you take a light bulb and connect one terminal of it to a battery nothing happens. If you complete the path by connecting the other terminal on the bulb to the other terminal on the battery, the light will light. Use this analogy in thinking about working with the electrical circuits in your home. If you felt comfortable enough to remove a wall plate from a duplex outlet you would see a white wire and a black wire. If the outlet is wired correctly, the black wire goes to the gold terminal and the white wire goes to the silver terminal. By convention, the black wire is the "hot" wire and the white wire is the common or neutral.
I must regress a bit here. Way back at the generating station, you know, the people that get a lot of your money each month for allowing you to have lights and toasters? Well, back there they took one wire from their generator and hooked it to the black wire and the other to the white wire. They also connected the white wire to ground - good old mother earth - you know, dirt! When that pair of wires comes into your home the white wire is once again connected to good old mother earth and the black wire to a circuit breaker and then on to the duplex outlet you are staring at.
Back to the duplex outlet. If one wanted to end it all one could simply grab the white wire with one hand and the black wire with the other, and it would be lights out - unlike what you would get if you connected the wires to a lamp. Notice I said both hands have to be involved - to complete the circuit.
Sooooo, if you weren't quite sure you wanted to end it all you could grab the black wire with one hand and just sit there contemplating your navel. Nothing would happen. Except that you would probably get bored after a while and go take a nap. On the other hand (no pun intended) if some other part of your body were in contact with, say a water pipe, which goes directly under the ground, the electric current would flow and you would be on your way to eternity.
One way people get zapped is to be holding on to the black wire and reach for a screwdriver that is resting on the sink or basin in contact with a faucet. See, the circuit is completed and they join the rest of the careless in lala land.
The lesson to be learned here is that one needs to be really careful that NO other part of the body is in contact with the ground portion of the house current circuit if one intends to be probing around in an electrical outlet box. Of course the real message here is that one should find the correct circuit breaker and switch it to the "off" position prior to removing the cover plate, however there is a small percentage of visitors in lala land who did follow that instruction only to find that they switched off the wrong breaker. Follow the rule - always - one hand works, nothing else touches ground - keep the other hand in your pocket!
One fallacy is that if your circuit is protected by a GFI, or Ground Fault Interrupter, you can't get hurt working on that circuit. Bull caca! You can get zapped just as dead, but you might have to work at it a bit harder.
Back to Brother Bob's Home Page
Copyright © 1996 by Bob Hewitt - All rights reserved