by Earl King

Created on: September 04, 2008

HOW ELECTRICITY IS GENERATED

Electricity is a form of energy. It can't be created or destroyed. It can only be converted from or to another form of energy. So let's explore where the energy comes from.

Heat energy can be produced from the splitting of atoms in a nuclear reactor. Heat can also be produced by burning wood, coal, oil or gas. These sources of heat can be used to raise the temperature of water, and if enough heat is applied, we get steam. This steam and the pressure it creates may be used to turn machines called turbines. The heat energy has become mechanical energy. The turbines will then turn other machines called generators. It is in this last machine, the generator, in which the mechanical energy is converted to electricity.

Another form of energy that works without using heat is potential energy. An example of potential energy is the water in a lake behind a dam. This form of storage is used at a hydroelectric plant, where the water stored in the lake will be released through special channels in the dam. The falling water impacts turbine blades, releasing its potential energy, converting it to mechanical energy. The turbine then turns a generator, converting mechanical energy into electric energy (generating alternating current electricity).

To go further in our understanding of how to generate electricity, we must take a look at magnetism. Position a bar magnet with the North Pole on the left and the South Pole on the right. The poles were so named because if you suspended the bar in the center, the North Pole would swing roughly toward earth's North Pole and the South Pole toward the earth's South Pole. Take a small compass and move it about the bar magnet. We see that the needle points in different directions depending on its position. If we map the area around the bar magnet, indicating the directions our compass gives, we have a picture of a magnetic field. This field could also be mapped by placing a thin sheet of cardboard above the bar. Sprinkle a uniform covering of iron filings and then tap the sheet. The filings will arrange themselves into a field map quite similar to the first one.

The magnetic field is represented by magnetic flux lines. The direction of the flux lines were determined by your small compass. Note that the flux lines exits the north pole of the bar magnetic and reenters the South Pole. The strength of the field is greatest adjacent to the bar magnet. Its strength will vary inversely as the square of the distance

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