Efficiency

Efficiency

Definition:
Efficiency describes how much of the input energy or power is transferred usefully.

Energy form:
$\text{Efficiency} = \frac{\text{useful energy output}}{\text{total energy input}}$

Power form:
$\text{Efficiency} = \frac{\text{useful power output}}{\text{total power input}}$

Percentage efficiency:
$(\%) \, \text{efficiency} = \text{efficiency} \times 100\%$

Key ideas:

• No device is 100% efficient
• Energy is conserved
• Wasted energy is transferred to the surroundings