What is meant by the efficiency of a machine?
If a machine is efficient it means the amount of usable energy it produces is not too much less than the energy it uses. For example, an efficient car is one which can travel for a very long time and distance on a small quantity of fuel. This is achieved by wasting as little of the energy in the fuel as possible. In this instance useful energy is that which is converted from chemical energy into motion. Any other energy given out (as heat or noise) is wasted.
