# 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).

## Efficiency of typical electrical devices

Efficiency should not be confused with effectiveness: a system that wastes most of its input power but produces exactly what it is meant to is effective but not efficient. The term "efficiency" only makes sense in reference to the wanted effect. So a light bulb might have 2% efficiency 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, apart from the small fraction that leaves through the windows). An electronic amplifier that delivers 10 watts of power to its load (for example a loudspeaker), while drawing 20 watts of power from a power source is 50% efficient. (10/20 Ã— 100% = 50%)
• Electric kettle: over 90% (comparatively little heat energy is lost during the 2 to 3 minutes a kettle takes to boil water).

## Efficiency of devices at point of Maximum Power Transfer

As a result of the Maximum Power Theorem, devices transfer maximum power to a load when running at 50% electrical efficiency. This occurs when the load resistance (of the device in question) is equal to the internal Thevenin equivalent resistance of the power source.

## Efficiency of light bulbs

For more details on this topic, see Luminous efficacy.

## Discussion

High efficiency is obviously desirable when we wish to design systems that can operate from batteries. Inefficiency has a cost (either paid to the power company or the cost of the required power supply) to be weighed against the cost of attaining greater efficiency (choosing different components or redesigning the system). Also, 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.

Device may refer to:

## Computing and electronics

• Computer hardware
• Peripheral device, any device attached to a computer that expands its functionality
• Device file, an interface for a device driver

An electronic component is a basic electronic element usually packaged in a discrete form with two or more connecting leads or metallic pads. Components are intended to be connected together, usually by soldering to a printed circuit board, to create an electronic circuit
System (from Latin systēma, in turn from Greek σύστημα systēma) is a set of entities, real or abstract, where each entity interacts with, or is related to, at least one other
Electronics is the study of the flow of charge through various materials and devices such as, semiconductors, resistors, inductors, capacitors, nano-structures, and vacuum tubes. All applications of electronics involve the transmission of power and possibly information.
Electrical engineering (sometimes referred to as electrical and electronic engineering) is an engineering field that deals with the study and/or application of electricity, electronics and electromagnetism.
expression must be well-formed. That is, the operators must have the correct number of inputs, in the correct places. The expression 2 + 3 is well formed; the expression * 2 + is not, at least, not in the usual notation of arithmetic.
Effectiveness means the capability of producing an effect.

In Physics, an effective theory is, similar to a phenomenological theory, a framework intended to explain certain (observed) effects without the claim that the theory correctly models the underlying (unobserved)
incandescent light bulb (also spelled lightbulb) or incandescent lamp is a source of artificial light that works by incandescence. An electrical current passes through a thin filament, heating it until it produces light.

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In electrical engineering, the maximum power (transfer) theorem states that, to obtain maximum power from a source with a fixed internal resistance, the resistance of the load must be made the same as that of the source.
In electrical circuit theory, ThÃ©venin's theorem for linear electrical networks states that any combination of voltage sources, current sources and resistors with two terminals is electrically equivalent to a single voltage source V and a single series resistor R.
Luminous efficacy is a property of light sources, which indicates what portion of the emitted electromagnetic radiation is usable for human vision. It is the ratio of emitted luminous flux to radiant flux.
incandescent light bulb (also spelled lightbulb) or incandescent lamp is a source of artificial light that works by incandescence. An electrical current passes through a thin filament, heating it until it produces light.
compact fluorescent lamp (CFL), also known as a compact fluorescent light bulb is a type of fluorescent lamp designed to replace an incandescent lamp. Many CFLs can fit in the existing incandescent light fixtures.
light-emitting diode (LED) is a semiconductor diode that emits incoherent narrow-spectrum light when electrically biased in the forward direction of the p-n junction. This effect is a form of electroluminescence.
Design, usually considered in the context of the applied arts, engineering, architecture, and other such creative endeavors, is used both as a noun and a verb. As a verb, "to design" refers to the process of originating and developing a plan for a product, structure, system, or
System (from Latin systēma, in turn from Greek σύστημα systēma) is a set of entities, real or abstract, where each entity interacts with, or is related to, at least one other
battery is a device consisting of one or more electrochemical cells, which store chemical energy and make it available in an electrical form. There are many types of electrochemical cells, including galvanic cells, electrolytic cells, fuel cells, flow cells, and voltaic cells.
power supply (sometimes called a power supply unit or PSU) is a device or system that supplies electrical or other types of energy to an output load or group of loads.
NOiSE is a one volume manga created by Tsutomu Nihei as a prequel to his acclaimed ten-volume work, Blame!.

It offers some rather sketchy information concerning the Megastructure's origins and initial size, as well as the origins of Silicon life.
''For other uses, see oscillator (disambiguation)
Oscillation is the variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states.
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Temperature is a physical property of a system that underlies the common notions of hot and cold; something that is hotter generally has the greater temperature. Temperature is one of the principal parameters of thermodynamics.
In electrical engineering, the maximum power (transfer) theorem states that, to obtain maximum power from a source with a fixed internal resistance, the resistance of the load must be made the same as that of the source.
Negawatt power is a term coined for an arbitrage way of supplying additional electrical energy to consumers without increased generation capacity by the creation of a market for trading of increased efficiency. The concept was introduced by Amory Lovins in a 1989 speech.
battery is a device consisting of one or more electrochemical cells, which store chemical energy and make it available in an electrical form. There are many types of electrochemical cells, including galvanic cells, electrolytic cells, fuel cells, flow cells, and voltaic cells.
Alphabetization has been neglected in some parts of this article (the "b" section in particular). You can help by editing it.

This is a list of communications, computers, electronic circuits, fiberoptics, microelectronics, medical electronics,