Electrical efficiency
The efficiency of an entity (a device, component, or system) in electronics and electrical engineering is defined as useful power output divided by the total electrical power consumed (a fractional expression).
- <math>\mathrm{Efficiency}=\frac{\mathrm{Useful\ power\ out}}{\mathrm{Total\ power\ consumed}}<math>
Efficiency should not be confused with light bulb might be 2% efficient at emitting light yet still be 98% efficient at heating a room. (In practice it is nearly 100% efficient at heating a room because the light energy will also be converted to heat eventually).
As an example: an electronic amplifier that delivers 10 Watts RMS of power to its load (for example a loudspeaker), while drawing 20 Watts of power from a power source is 50% efficient. (10/20 x 100% = 50%)
Efficiency of typical electrical devices
Efficiency is an obvious consideration when we wish to design systems that can operate from batteries. For more subtle reasons, the same is true when the amounts of power are large: any difference in the input and output power probably produces heat within the system (though noise and other mechanical vibrations involve at least theoretically separate inefficiencies), and that heat must be removed from the system if it is to remain within its operating temperature range. And in general, since power is seldom free, every inefficiency in effect gets its costs (either paid to the power company or the cost of the required power supply) weighed against the cost of attaining greater efficiency (choosing different components or redesigning the system).
See also
