Volt – This is the unit of pressure in the electrical system. It is abbreviated as V. To have 10V is like having 10 pounds of water pressure. The more volts you have, the more electricity will be forced to flow, and the more dangerous the system becomes. The number of volts which you use is important when you ask for wire to add to your home circuits, or install new circuits in your home. As you can readily imagine, if you use a wire which has a covering (insulation) designed to contain 10V, this same covering will rupture if you apply a 120V pressure to it. Always be sure to buy wire which has a UL label showing it is tested for the voltage you plan to use it on.
This analogy might be useful if you are completely unfamiliar with electricity. If you have a water pipe and the wall of the pipe is too thin to withstand the internal water pressure, the pipe will rupture. With electricity, the insulation covering the wire is like the wall of the pipe. If the insulation has insufficient strength for the voltage pressure applied, then electrical short circuits, groundings, sparks, heating, blown fuses, etc., may result. Handling such a live wire may permit the electricity to leap from the wire into your body. You must be always very careful when required to handle a live electrical wire. It can kill you!
Remember, when you buy wire for your home or office electrical circuits, be sure it has the proper volts value. It is customary to use wire which is insulated for 600V for all home and office wiring. Ask your dealer about this.
Ampere – This is the flow term. It is abbreviated as A. It represents how much electricity is used each second. Here again we can imagine a pipe carrying water. If we want a fast flow, that is, a large number of galloons per minute through a pipe, then we use a large diameter pipe. With electricity, if we want a large flow, we use a large diameter wire. Any time we do not provide sufficient diameter pathway for the flow of electricity, the wire will get hot. It may burn and cause a fire if proper precautions are not used in installation. Always use the right diameter wire for the circuit.
Wire sizes – Electrical wires are specified in terms of how many amperes can pass through them without overheating. For 15 to 20A circuits, such as in your homes, wire sizes are No. 12 and 14. For larger currents, sizes 10 and 8 are sometimes used. Notice that the wire size is larger as the number becomes smaller. For example, a wire size of 1 is much larger than a wire size of 22. In your electrical extension cords, the wire size is generally about 18 and this size can safely pass a current of 10A. Incidentally, there is a group of stranded wires so arranged that they all touched each other, so they are bunched, then their size is equivalent to a solid wire of copper having the same diameter. The stranding just gives flexibility.
Watt – This is the power term. It is abbreviated as W. It represents how much equivalent heat the volts and amperes produce if connected to an appliance. It represents how much energy is dissipated as light and heat from a light bulb. It is a measure of power consumed. Watts are determined by multiplying the volts by the amperes. The formula is W=VxA.
This is important to us because if we plan to use an appliance which has a rating of 240W at 120V, then we can find the amperes which the current will have to be able to pass. Since the original formula is W=VxA, we must transpose to find A. By algebraic manipulation, the formula becomes A=W/V. We then plug in the numbers and we have 240W/120V=2A.
By the way, 240W is about right for a small tube-type TV set. Since most home outlets individually are connected to pass at least 15A, if nothing else is on the circuit, we can use the TV and other appliances or lights on the circuit without problems. If you use a flatiron and the rating is 1000W, then note that the current is high: 1000W/120V=8.33A. This is about the most current you should expect to pass through an 18-gage cord without excessive heating and its resultant power waste.
Watts is the rate of use of electrical power. Here is a definition to explain watts in terms of the amount of work they can do for you. One horsepower is equal to 550W. One horsepower is equal to 33,000 foot pounds. This means the energy it takes to raise a load of 33,000 pounds a height of one foot. One horsepower is also the effort of one strong, fast horse pulling 330 pounds up out of a well that’s 100 feet deep in 1 minute.