What is power? - Definition from WhatIs.com
Part of the Electronics glossary:

Also see current, voltage, resistance,and Ohm's Law.

Electrical power is the rate at which electrical energy is converted to another form, such as motion, heat, or an electromagnetic field. The common symbol for power is the uppercase letter P. The standard unit is the watt,symbolized by W. In utility circuits, the kilowatt (kW) is often specified instead;1 kW = 1000 W.

One watt is the power resulting from an energy dissipation, conversion, or storage process equivalent to one joule per second. When expressed in watts, power is sometimes called wattage. The wattage in a direct current (DC) circuit is equal to the product of the voltage in volts and the current in amperes. This rule also holds for low-frequency alternating current (AC) circuits in which energy is neither stored nor released. At high AC frequencies, in which energy is stored and released (as well as dissipated or converted), the expression for power is more complex.

In a DC circuit, a source of E volts, deliveringIamperes, produces P watts according to the formula:

P = EI

When a current of I amperes passes through a resistance of Rohms, then the power in watts dissipated or converted by that component is given by:

P = I2R

When a potential difference of E volts appears across a component having a resistance of R ohms, then the power in watts dissipated or converted by that component is given by:

P = E2/R

In a DC circuit, power is a scalar (one-dimensional) quantity. In the general AC case, the determination of power requires two dimensions, because AC power is a vector quantity. Assuming there is no reactance (opposition to AC but not to DC) in an AC circuit, the power can be calculated according to the above formulas for DC, using root-mean-square values for the alternating current and voltage. If reactance exists, some power is alternately stored and released by the system. This is called apparent power or reactive power. The resistance dissipates power as heat or converts it to some other tangible form; this is called true power. The vector combination of reactance and resistance is known as impedance.

This was last updated in January 2008
Contributor(s): Jerome Kelly
Posted by: Margaret Rouse

Related Terms

Definitions

  • frequency-hopping spread spectrum

    - Frequency hopping is one of two basic modulation techniques used in spread spectrum signal transmission. (SearchNetworking.com)

  • robot

    - A robot is a machine designed to execute one or more tasks automatically with speed and precision. There are as many different types of robots as there are tasks for them to perform. (WhatIs.com)

  • matter

    - Matter is a substance that has inertia and occupies physical space. (WhatIs.com)

Glossaries

  • Electronics

    - Terms related to electronics, including definitions about electrical components and words and phrases about computers, laptops parts, digital cameras, televisions and home appliances.

  • Internet applications

    - This WhatIs.com glossary contains terms related to Internet applications, including definitions about Software as a Service (SaaS) delivery models and words and phrases about web sites, e-commerce ...

Ask a Question. Find an Answer.Powered by ITKnowledgeExchange.com

Ask An IT Question

Get answers from your peers on your most technical challenges

Ask Question
  • BRMS configuration

    Check your devices in BRMS (WRKDEVBRM). Each device is linked with a location.

  • Send CPF1816/1817 by Program without a UPS attached

    I did some testing like you are describing in a previous employment (but that was 10 years ago).  The messages/message IDs for testing have to be put into the same message queue bein...

  • Control USB power supply in Linux

    If you do a web search on your question, you will find a list of sites that can assist you. Here is one of them. http://stackoverflow.com/questions/4702216/controlling-a-usb-power-supply-on-off-wit...

Tech TalkComment

Share
Comments

    Results

    Contribute to the conversation

    All fields are required. Comments will appear at the bottom of the article.