Question

Why is a machine not 100% efficient?

Answer 1

Ideal machine:

1. An ideal machine is a machine whose parts are weightless and frictionless.
2. Thus there is no dissipation of energy in any manner. Its efficiency is 100%, i.e. the work output is equal to work input.
3. Ideal machine can also be stated as a machine in which no part of the work done on the machine is wasted.
4. Mathematically it can be stated as, $Workinput=Workoutout$.

An ideal machine differing from a practical machine:

1. Ideal machine is originally a hypothetical mechanical system in which energy and power are not lost or dissipated through friction.
2. The efficiency of an ideal machine should be 100% but the efficiency of a practical machine is always less than 100% according to the second law of thermodynamics.
3. The second law of thermodynamics states that as energy is transferred or transformed, more and more of it is wasted.
4. A machine cannot be 100 per cent efficient because the output of a machine is always less than the input.
5. A certain amount of work done on a machine is lost to overcome friction and to lift some moving parts of the machine.
6. Ideal machines are said to have parts that are weightless and frictionless but practical machines have parts that have weights and friction.

Hence, a machine cannot be 100% efficient because the output of a machine is always less than the input.