Efficiency

EFFICIENCY:

Efficiency is defined as the ratio of output to the input is called Efficiency. Efficiency is denoted by symbol $\eta$.

EXPLANATION:

Consider a system in which some energy ‘$E_1$’ is supplied to it as an ‘input’ and the system returns back some energy ‘$E_2$’ as output. the expression for efficiency of such system is given as follows:

$Efficiency = \frac {\;output \;energy}{ input energy }$

Or

$\% \eta = \frac {E_{output}}{E_{input}} \times 100$

$\boxed{\%\eta= \frac{E_1}{E_2} \, \text{x} \,100}$

• As it is the ratio of two energies therefore it has no unit.

• No machine is 100% efficient because some energy is always wasted in the form of heat, sound or light etc.

Example

INPUT: We give electric energy as input to the electric motor in washing machines and in drilling machines.

OUTPUT: The output is the motor moving the load.

LOSS: Energy is wasted in the form of heat and sound.