Useful Energy Conversions by Harcourt Achieve Inc

Useful Energy Conversions Worksheet

The law of conservation of energy states that energy is neither made nor destroyed. It only changes form. Think of the electrical energy that comes into your home. It may have been generated by falling water. The falling water has kinetic energy. When it falls against a turbine, the turbine starts to spin. The turbine is attached to the rotor of an electric generator. Here, kinetic energy is converted into electrical energy (see figure below). The electrical energy is carried over power lines to your home. What happens to it here? It is converted into many different forms of energy. Irons, toasters, and ovens convert the electrical energy into heat energy. Fans, mixers, and blenders convert electrical energy into mechanical energy. Radios convert electrical energy into sound energy.

Although no energy is created or destroyed as it changes from one form to another, useful energy is lost along the way. For example, what happens to a radio or television when it is on for a while? It gets warm. Some of the electrical energy is converted into useless heat energy. This useless heat energy is the result of friction. Friction is a force, usually produced by rubbing, that resists motion. In this case, the electricity rubs against the wires as it moves through them. This causes the wires to heat up.