efficiency of a machine In thermodynamics and the theory of machines, the ratio of the useful work derived from a machine to the energy put into it. The mechanical efficiency of a machine is always less than 100%, some energy being lost as heat in friction. When the machine is a heat engine, the theoretical thermal efficiency can be found from the second law of thermodynamics but actual values are often rather lower. A typical gasoline engine may have a thermal efficiency of only 25%, a steam engine 10%. Related category CLASSICAL MECHANICS Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) |