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Worldwide distribution of country calling codes. Regions are coloured by first digit. Country calling codes, country dial-in codes, international subscriber dialing (ISD) codes, or most commonly, telephone country codes are telephone number prefixes for reaching telephone subscribers in foreign countries or areas via international telecommunication networks.
The resistivity can be expressed using the SI unit ohm metre (Ω⋅m) — i.e. ohms multiplied by square metres (for the cross-sectional area) then divided by metres (for the length).Both resistance and resistivity describe how difficult it is to make electrical current flow through a material, but unlike resistance, resistivity is an intrinsic property and does not depend on geometric ...
- Overview
- Origin and Adoption as An Si Unit
- Multiples
- Conventions in The Electric Power Industry
- Radio Transmission
- Distinction Between Watts and watt-hours
- See Also
- External Links
When an object's velocity is held constant at one meter per second against a constant opposing force of one newton, the rate at which workis done is one watt. In terms of electromagnetism, one watt is the rate at which electrical work is performed when a current of one ampere (A) flows across an electrical potential difference of one volt (V), mean...
The watt is named after the Scottish inventor James Watt. The unit name was proposed by C. William Siemens in August 1882 in his President's Address to the Fifty-Second Congress of the British Association for the Advancement of Science. Noting that units in the practical system of units were named after leading physicists, Siemens proposed that wat...
Attowatt
1. The sound intensity in water corresponding to the international standard reference sound pressure of 1 μPa is approximately 0.65 aW/m2.
Femtowatt
1. Powers measured in femtowatts are typically found in references to radio and radar receivers. For example, meaningful FM tuner performance figures for sensitivity, quieting and signal-to-noise require that the RF energy applied to the antenna input be specified. These input levels are often stated in dBf (decibels referenced to 1 femtowatt). This is 0.2739 microvolts across a 75-ohm load or 0.5477 microvolt across a 300-ohm load; the specification takes into account the RF input impedanceo...
Picowatt
1. Powers measured in picowatts are typically used in reference to radio and radar receivers, acoustics and in the science of radio astronomy. One picowatt is the international standard reference value of sound powerwhen this quantity is expressed in decibels.
In the electric power industry, megawatt electrical (MWe or MWe) refers by convention to the electric power produced by a generator, while megawatt thermal or thermal megawatt (MWt, MWt, or MWth, MWth) refers to thermal power produced by the plant. For example, the Embalse nuclear power plant in Argentina uses a fission reactor to generate 2,109 MW...
Radio stations usually report the power of their transmitters in units of watts, referring to the effective radiated power. This refers to the power that a half-wave dipole antenna would need to radiate to match the intensity of the transmitter's main lobe.
The terms power and energy are closely related but distinct physical quantities. Power is the rate at which energy is generated or consumed and hence is measured in units (e.g. watts) that represent energy per unit time. For example, when a light bulb with a power rating of 100W is turned on for one hour, the energy used is 100 watt hours (W·h), 0....
Media related to Wattat Wikimedia CommonsThe dictionary definition of wattat WiktionaryBorvon, Gérard. "History of the electrical units".Nelson, Robert A. (February 2000). The International System of Units: Its History and Use in Science and Industry. Via Satellite. ATI courses.The symbol # is known variously in English-speaking regions as the number sign,[1] hash,[2] or pound sign.[3] The symbol has historically been used for a wide range of purposes including the designation of an ordinal number and as a ligatured abbreviation for pounds avoirdupois – having been derived from the now-rare ℔.[4] Since 2007 ...
Transformer. An O-core transformer consisting of two coils of copper wire wrapped around a magnetic core. In electrical engineering, a transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying ...
Four UN members (Cuba, Liechtenstein, Monaco and North Korea) do not belong to the IMF hence their economies are not ranked below. Kosovo, despite not being a member of the United Nations, is a member of IMF. Taiwan is not a IMF member but it is still listed in the official IMF indices. Several leading GDP-per-capita (nominal) jurisdictions may ...
Different lengths as in respect to the electromagnetic spectrum, measured by the metre and its derived scales.The microwave is between 1 meter to 1 millimeter. The millimetre (international spelling; SI unit symbol mm) or millimeter (American spelling) is a unit of length in the International System of Units (SI), equal to one thousandth of a metre, which is the SI base unit of length.
