Darin Michalski, age 8, of Willow Lake, South Dakota, for his question:
HOW FAST DOES ELECTRICITY TRAVEL?
Electricity goes to more than 90 percent of the homes in the United States and to more than 80 percent of those in Canada. Modern industry couldn't exist without electricity since it must be available for lighting, motors, drills, lathes, milling machines and lots of tools. Electricity is used to operate cranes that lift huge loads and to power delicate electronic instruments.
Electricity is a form of energy. It gives us light, heat and power.
Electrical energy, or the ability of electricity to do work, travels through a wire almost as fast as the speed of light, which is 186,282 miles a second. When you talk into a telephone, the person on the other end of the wire hears your voice almost instantly.
Electric current in a wire works very much like a long hose that is filled with water. If you connect the hose to a faucet and turn the water on and off, spurts of water come out of the far end of the hose almost immediately. You will have sent a signal from one end to the other, though any drop of water in the hose will have moved a much shorter distance.
In order to conduct electricity, the atoms of a substance must have electrons that are free to move from atom to atom. Metals have such free electrons, and so metals make good conductors of electricity. Only the electrons move in metal conductors.
Electrons are among the smallest known particles. In a 60 watt light bulb, about 3 billion billion electrons a second flow past any point in the wires to the bulb. These electrons travel slowly from atom to atom in the wires, but the energy moves almost as fast as the speed of light. Three billion billion, by the way, is the number 3 followed by 18 zeros.
The flow of electric current and of water both depend on three factors: the pressure that causes the current to flow, the rate of flow and the resistance of the wire or hose to the flow.
Both the flow of electric current and of water produce power. In electricity, the units used to measure these factors are volts for pressure, amperes for the amount or rate of current flow, ohms for resistance and watts for power.
Electrons travel through any conductor from a negative source to a positive source of electricity. There are two main kinds of electric current: direct and alternating.
Direct current flows in only one direction while alternating current rapidly reverses its direction of flow many times a second.
Electricity flowing through a wire sets up a magnetic field about the wire. Electric generators produce most of the world's electricity by whirling powerful magnets past coils of copper bars.