English V. [antikvár]

Energy is considered to be the power to do things. So far different forms of energy ha ve been taken into account. There is, for example, that form of energy which is called heat, there is alsó chemical energy, mechanical energy and electrical energy. Now any form of energy can be changed into another form. If eoal is burned to make steam, the burning of the coal supplies heat energy to water in a steam-boiler. The steam may be led into an engine producing mechanical energy. This in its turn may drife a dynamo producing electrical energy. This electrical energy may be changed into radiant energy of an electrical lamp. Electrical energy can be changed back into mechanical energy by an electric motor. Though no energy is ever lost in the universe, being its energy quantity always constant, this transformation