Question

Explain why the efficiency of a machine is never 100%.

Answer 1

1. The efficiency of a machine can be defined as-
   $$\begin{gathered} Efficiency=\frac{workdonebymachine}{workdoneonmachine}=\frac{outputenergy}{inputenergy} \\ Efficiency\%=\frac{outputenergy}{inputenergy}\times 100 \end{gathered}$$
2. In other words, we can say that the efficiency of a machine shows how effectively its input energy gets converted to useful work.
3. All the input energy is not converted into output energy as some of the input energy is lost in heat and friction.
4. Therefore output energy is always less than input energy which makes efficiency less than 100%.
5. However, in the case of an ideal machine (which does not generate heat and friction) efficiency is100 %.