The efficiency of machines is usually expressed in?

Answer 1

Efficiency is expressed as a factor, like 0.9, or a percentage - the above is equivalent to 90%. An efficiency of 90% means that 90% of the input energy (or a factor of 0.9) is converted into whatever you want to convert it to; the remainder is wasted.

Answer 2

The efficiency of machines is usually expressed in terms of the ratio of the useful work output to the total energy input. It is typically calculated as a percentage, with higher percentages indicating more efficient machines.