Micro-hydro: Making electricity

We are surrounded by hundreds of appliances that use electricity to do work. But what is electricity? Basically, electricity is a flow of electrons in a metal wire, or some other conductor. Electrons are tiny particles found inside atoms, one of the basic building blocks of all matter. We call the flow of electrons through any conductor a “current of electricity.”

Each electron carries a tiny negative charge. When electrons move through a conductor, they produce an invisible field of magnetic force, similar to that found around a magnet. The strength of that field depends on how many electrons are in motion. You can concentrate this field by winding the wire in which the electrons move into a tight coil with many turns. This causes many more electrons to be in motion in a small space, resulting in a stronger field. If you then place a piece of iron in the middle of the coil, the electromagnetic field will turn the iron into a powerful magnet.

While it is true that electrons moving through a conductor produce a magnetic field, the reverse is also true. You can make electrons move in a wire by “pushing” them with a moving magnet, which is how an electrical generator works. Electrical generators usually contain powerful magnets that rotate very close to dense coils of insulated wire. The coils develop a flow of electrons that becomes an electrical current when the generator is connected to an electric circuit.

We will be building an electrical generator as part of this project.  It uses moving magnets to create a current of electricity in coils of wire. This generator is technically called an alternator because the electrons move back and forth in the wire, rather than flowing in just one direction as they do from a battery. A meter connected to the wire would show that the charge of the wire switches or alternates between positive and negative as the electrons change directions. Such an electrical current is called alternating current or AC. Household electrical current is alternating current. Appliances have to be specially designed to use it. The other type of current is called direct current, because the electrons move in one direction only. Most battery-powered appliances such as calculators and portable CD players use direct current.