SI - Article Index

Encyclopedia - Si: Encyclopedia Ii - Si - History
The metric system was created during the French Revolution. On August 1, 1793 the National Convention adopted the new decimal "metre" wit...   » Read the article

Encyclopedia - Si: Encyclopedia Ii - Si - History
The metric system was officially adopted in France after the French Revolution. During the history of the metric system a number of varia...   » Read the article

Encyclopedia - Watt: Encyclopedia - Watt
The watt (symbol: W) is the SI derived unit of power. Watt - Definition. One watt is one joule of energy per second. 1 W = 1 J/s = 1 ne...   » Read the article

Encyclopedia - Conversion Of Units: Encyclopedia - Conversion Of Units
This article lists conversion factors between a number of units of measurement. Conversion of units - Conversion techniques. The simples...   » Read the article

Encyclopedia - Coulomb: Encyclopedia - Coulomb
The coulomb (symbol: C) is the SI unit of electric charge. It is named after Charles-Augustin de Coulomb (1736 to 1806). Coulomb - Defini...   » Read the article

Encyclopedia - Weights And Measures: Encyclopedia - Weights And Measures
Weights and measures is a term used by legal authorities in English speaking countries such as the United Kingdom for a function related ...   » Read the article

Encyclopedia - Units Of Measurement: Encyclopedia - Units Of Measurement
The definition, agreement and practical use of units of measurement have played a crucial role in human endeavour from early ages up to t...   » Read the article

Encyclopedia - Metre: Encyclopedia - Metre
The metre (Commonwealth English) or meter (American English) (symbol: m) is the SI base unit of length. It is defined as the length of th...   » Read the article

Encyclopedia - Force: Encyclopedia - Force
In physics, a force is an external cause responsible for any change of a physical system. For instance, a person holding a dog by a rope ...   » Read the article

Encyclopedia - Ampere: Encyclopedia - Ampere
The ampere (symbol: A) is the SI base unit of electrical current equal to one coulomb per second. It is named after André-Marie Ampère,...   » Read the article

Encyclopedia - Systems Of Measurement: Encyclopedia - Systems Of Measurement
Metric systems of units have evolved since the adoption of the first well-defined system in France in 1791. During this evolution the use...   » Read the article

Encyclopedia - Codata: Encyclopedia - Codata
CODATA (Committee on Data for Science and Technology) was established in 1966 as an interdisciplinary committee of the International Coun...   » Read the article

Encyclopedia - U.s. Customary Units: Encyclopedia - U.s. Customary Units
U.S. customary units, commonly known in the United States as English units or standard units, are units of measurement that are currently...   » Read the article

Encyclopedia - Foot Unit Of Length: Encyclopedia - Foot Unit Of Length
A foot (plural: feet) is a non-SI unit of distance or length, measuring around a third of a metre. There are twelve inches in one foot an...   » Read the article

Encyclopedia - French Units Of Measurement: Encyclopedia Ii - French Units Of Measurement - French System
In France, again, there were many local variants. For instance, the lieue could vary from 3.268 km in Beauce to 5.849 km in Provence. Bet...   » Read the article

Encyclopedia - Spanish Units Of Measurement: Encyclopedia Ii - Spanish Units Of Measurement - Spanish System
There were several variants. The Castilian is shown. Spanish units of measurement - Length. punto – point, 1 / 12 línea línea – ...   » Read the article

Encyclopedia - Si Derived Unit: Encyclopedia Ii - Si Derived Unit - Conversion Between Kelvins And Degrees Celsius
A change in temperature of 1°C is equal to a change in temperature of 1K. Temperature in °C = Temperature in kelvins - 273.15 Thus, one...   » Read the article

Encyclopedia - Systems Of Measurement: Encyclopedia Ii - Systems Of Measurement - The Metric System
Metric systems of units have evolved since the adoption of the first well-defined system in France in 1791. During this evolution the use...   » Read the article

Encyclopedia - Units Of Measurement: Encyclopedia Ii - Units Of Measurement - Calculations With Units
Units of measurement - Units as dimensions. Any value of a physical quantity is expressed as a comparison to a unit of that quantity. F...   » Read the article

Encyclopedia - Norwegian Units Of Measurement: Encyclopedia Ii - Norwegian Units Of Measurement - Length
Norwegian units of measurement - Nautical. favn – fathom (pl. favner), 3 alen, 1.88 m kabellengde – cable length, 100 favner188 m,...   » Read the article

Encyclopedia - German Units Of Measurement: Encyclopedia Ii - German Units Of Measurement - Length
Rute (rod): Carolingian origin, use as land measure. e.g. - Saxony (Sachsen) : 1 alte Rute = 1 Feldmesser-Rute = 7.5 Ellen = 4.295...   » Read the article

Encyclopedia - A: Encyclopedia - A
The letter A is the first letter in the Latin alphabet. Its name in English is a, plural ās or aes. A - History. The letter A probably...   » Read the article

Encyclopedia - Ampere: Encyclopedia Ii - Ampere - Explanation
Because it is a base unit, the definition of the ampere is not tied to any other electrical unit. The definition for the ampere is equiva...   » Read the article

Encyclopedia - Acceleration: Encyclopedia - Acceleration
In physics, acceleration (symbol: a) is defined as the rate of change (or time derivative) of velocity. It is thus a vector quantity with...   » Read the article

Encyclopedia - U.s. Customary Units: Encyclopedia Ii - U.s. Customary Units - Units Of Mass
There have historically been four different English systems of mass: Tower weight, Troy weight, Avoirdupois system, and Apothecaries' sys...   » Read the article

Encyclopedia - Comparison Of The Imperial And U.s. Customary Systems: Encyclopedia Ii - Comparison Of The Imperial And U.s. Customary Systems - Volume
The Imperial gallon (4.546 09 litres (L)) and bushel (36.368 72 L) are, respectively, about 20 per cent and 3 per cent larger than the Un...   » Read the article

Encyclopedia - Si Derived Unit: Encyclopedia Ii - Si Derived Unit - Conversion Between Kelvins And Degrees Celsius
A change in temperature of 1°C is equal to a change in temperature of 1K. Temperature in °C = Temperature in kelvins - 273.15 Thus, one...   » Read the article

Encyclopedia - Angstrom: Encyclopedia - Angstrom
An angstrom, angström, or ångström (symbol Å) is a unit of length. It is not an SI unit. It is accepted (although discouraged) for us...   » Read the article

Encyclopedia - Coulomb: Encyclopedia Ii - Coulomb - Explanation
The coulomb is also the unit of electric flux. (See Gauss Law). The coulomb could in principle be defined in terms of the charge of an el...   » Read the article

Encyclopedia - Force: Encyclopedia Ii - Force - Quantitative Definition
In physics models, the point-like system is used, where objects are represented as one-dimensional points at their centre of mass. The on...   » Read the article

Encyclopedia - Conversion Of Units: Encyclopedia Ii - Conversion Of Units - Conversion Techniques
The simplest way to convert from one unit to another is to carry through the units themselves in the mathematical operation. To illustrat...   » Read the article

Encyclopedia - Systems Of Measurement: Encyclopedia Ii - Systems Of Measurement - The Metric System
Metric systems of units have evolved since the adoption of the first well-defined system in France in 1791. During this evolution the use...   » Read the article

Encyclopedia - Ampere: Encyclopedia Ii - Ampere - Explanation
Because it is a base unit, the definition of the ampere is not tied to any other electrical unit. The definition for the ampere is equiva...   » Read the article

Encyclopedia - Metre: Encyclopedia Ii - Metre - History
The word metre is from the Greek metron (μετρον), "a measure" via the French mètre. Its first recorded usage in English is from 17...   » Read the article

Encyclopedia - History Of Measurement: Encyclopedia Ii - History Of Measurement - History Of Units
History of measurement - Units of length. The Indus Valley units of length referred to above and the Mesopotamian cubit were both used ...   » Read the article

Encyclopedia - Watt: Encyclopedia Ii - Watt - Derived And Qualified Units For Power Distribution
A watt is a unit of power or the amount of energy per unit time. Watt - Kilowatt-hour MWd. When paired with a unit of time the term wat...   » Read the article

Encyclopedia - Square Metre: Encyclopedia Ii - Square Metre - Square Kilometre
1 km² is equal to: the area of a square measuring 1 kilometre on each side 1,000,000 m² 100 hectares 0.386 102 square miles (statute) ...   » Read the article

Encyclopedia - Kilometre: Encyclopedia Ii - Kilometre - Metric System
Like the kilometre, all units of length in the metric system are based on the metre, by adding an SI prefix that stands for a power of te...   » Read the article

Encyclopedia - English Unit: Encyclopedia Ii - English Unit - Historical English Units
English unit - Length. poppyseed  ¼ of a barleycorn barleycorn  Basic Anglo-Saxon unit, the length of a corn of barley. The...   » Read the article

Encyclopedia - Kilogram: Encyclopedia Ii - Kilogram - History
The kilogram was originally defined as the mass of one litre of pure water at a temperature of 3.98 degrees Celsius and standard atmosphe...   » Read the article

Encyclopedia - Architect's Scale: Encyclopedia - Architect's Scale
An architect's scale is a specialized ruler. It is used in making or measuring from reduced scale drawings, such as blueprints. It is mar...   » Read the article

Encyclopedia - Anticyclone: Encyclopedia - Anticyclone
In meteorology, an anticyclone (i.e. opposite to a cyclone) is a weather phenomenon in which there is a descending movement of the air an...   » Read the article

Encyclopedia - Are: Encyclopedia - Are
For the municipality in Sweden, see Åre; for the boroughtown and rural municipality in Estonia see Are; for the language from Papua New ...   » Read the article

Encyclopedia - Gravity: Encyclopedia - Gravity
Gravity is a force of attraction that acts between bodies that have mass. It is a physical phenomenon of fundamental importance, profoun...   » Read the article

Encyclopedia - Capacitance: Encyclopedia - Capacitance
Capacitance is a measure of the amount of electric charge stored (or separated) for a given electric potential. The capacitance is usuall...   » Read the article

Encyclopedia - Calorie: Encyclopedia - Calorie
A calorie is a unit of measurement for energy. In most fields, it has been replaced by the joule, the SI unit of energy. However, it rema...   » Read the article

Encyclopedia - Calcium Oxide: Encyclopedia - Calcium Oxide
General Physical Thermochemistry Safety SI units were used where possible. Unless otherwise stated, standard conditions were used. Discla...   » Read the article

Encyclopedia - Calcium Fluoride: Encyclopedia - Calcium Fluoride
General Physical properties SI units were used where possible. Unless otherwise stated, standard conditions were used. Disclaimer and ref...   » Read the article

Encyclopedia - Capacitor: Encyclopedia - Capacitor
A capacitor is a device that stores energy in the electric field created between a pair of conductors on which equal but opposite electri...   » Read the article

Encyclopedia - Centi: Encyclopedia - Centi
Centi can also stand for Centro Internacional de Teoterapia Integral (Integrated God-centered Therapy International Center). Centi (symbo...   » Read the article

Encyclopedia - Dash: Encyclopedia - Dash
apostrophe ( ' ) ( ’ ) brackets ( ( ) ) ( [ ] ) ( { } ) ( 〈 〉 ) colon ( : ) comma ( , ) dashes ( ‒ ) ( – ) ...   » Read the article

Encyclopedia - Non-si Unit Prefix: Encyclopedia - Non-si Unit Prefix
There exist several unit prefixes used like the SI prefixes, but that are not part of the SI system. Some of these were never part of any...   » Read the article

Encyclopedia - Characteristic Impedance: Encyclopedia - Characteristic Impedance
In radio communications, characteristic impedance (acoustic impedance or sound impedance) of a uniform transmission line is the impedanc...   » Read the article

Encyclopedia - Zepto: Encyclopedia - Zepto
Zepto (symbol z) is a prefix in the SI system of units denoting a factor of 10-21. Adopted in 1991, it comes from the French sept or Lati...   » Read the article

Encyclopedia - Zetta: Encyclopedia - Zetta
Zetta (symbol Z) is a SI prefix in the SI (system of units) denoting 1021 or 1 000 000 000 000 000 000 000. Adopted in 1991, it comes fro...   » Read the article

Encyclopedia - Centimetre Gram Second System Of Units: Encyclopedia - Centimetre Gram Second System Of Units
The centimetre-gram-second system (CGS) is a system of physical units. It is always the same for mechanical units, but there are several ...   » Read the article

Encyclopedia - General Conference On Weights And Measures: Encyclopedia - General Conference On Weights And Measures
The General Conference on Weights and Measures is the English name of the Conférence générale des poids et mesures (CGPM, never GCWM)....   » Read the article

Encyclopedia - Sodium Bicarbonate: Encyclopedia - Sodium Bicarbonate
SI units were used where possible. Unless otherwise stated, standard conditions were used. Disclaimer and references Sodium bicarbonate (...   » Read the article

Encyclopedia - Bar Unit: Encyclopedia - Bar Unit
The bar (symbol bar) and the millibar (symbol mbar, also mb) are units of pressure. They are not SI units, but accepted (although discour...   » Read the article

Encyclopedia - British Thermal Unit: Encyclopedia - British Thermal Unit
The British thermal unit (BTU or Btu) is a unit of energy still used in the United States. It is also still occasionally encountered in t...   » Read the article

Encyclopedia - Avogadro's Number: Encyclopedia - Avogadro's Number
Avogadro's number, also called Avogadro's Constant (NA) is a large constant used in chemistry and physics. Avogadro's number is formally ...   » Read the article

Encyclopedia - Astronomical Unit: Encyclopedia - Astronomical Unit
The astronomical unit (AU or au or a.u. or sometimes ua) is a unit of distance, approximately equal to the mean distance between Earth an...   » Read the article

Encyclopedia - Atomic Clock: Encyclopedia - Atomic Clock
An atomic clock is a type of clock that uses an atomic resonance frequency standard as its counter. Early atomic clocks were masers with ...   » Read the article

Encyclopedia - Universal Time: Encyclopedia - Universal Time
Universal Time (UT) is a timescale based on the rotation of the Earth. It is a modern continuation of the Greenwich Mean Time (GMT), i.e....   » Read the article

Encyclopedia - Barn Unit: Encyclopedia - Barn Unit
A barn (symbol b) is a unit of area. While the barn is not an SI unit, it is accepted (although discouraged) for use with the SI. It is u...   » Read the article

Encyclopedia - International Bureau Of Weights And Measures: Encyclopedia - International Bureau Of Weights And Measures
The International Bureau of Weights and Measures is the English name of the Bureau international des poids et mesures (BIPM, often writte...   » Read the article

Encyclopedia - Byte: Encyclopedia - Byte
A byte is commonly used as a unit of storage measurement in computers, regardless of the type of data being stored. It is also one of th...   » Read the article

Encyclopedia - Boltzmann Constant: Encyclopedia - Boltzmann Constant
The Boltzmann constant (k or kB) is the physical constant relating temperature to energy. It is named after the Austrian physicist Ludwig...   » Read the article

Encyclopedia - Benzoyl Peroxide: Encyclopedia - Benzoyl Peroxide
SI units were used where possible. Unless otherwise stated, standard conditions were used. Disclaimer and references Benzoyl peroxide is ...   » Read the article

Encyclopedia - Benzalkonium Chloride: Encyclopedia - Benzalkonium Chloride
General Physical Thermochemistry Safety SI units were used where possible. Unless otherwise stated, standard conditions were used. Discl...   » Read the article

Encyclopedia - Second Moment Of Area: Encyclopedia - Second Moment Of Area
The second moment of area, also known as the second moment of inertia and the area moment of inertia, is a property of a shape that is us...   » Read the article

Encyclopedia - Ammonium Perchlorate: Encyclopedia - Ammonium Perchlorate
General Physical Thermochemistry Safety SI units were used where possible. Unless otherwise stated, standard conditions were used. Discla...   » Read the article

Encyclopedia - Heat: Encyclopedia - Heat
Heat (also improperly called heat change) is a transient form of energy. It quantifies the spontaneous transfer of thermal energy due to ...   » Read the article

Encyclopedia - H: Encyclopedia - H
H is the eighth letter of the Latin alphabet. Its name in English is aitch. In the International Phonetic Alphabet, this symbol is used t...   » Read the article

Encyclopedia - G: Encyclopedia - G
G is the seventh letter in the Roman alphabet. Its name in English is gee. G - History. The letter G was created by the Romans because t...   » Read the article

Encyclopedia - K: Encyclopedia - K
The eleventh letter of the Latin alphabet, K, or k comes from the Greek Κ or κ (Kappa) developed from the Semitic Kap, symbol for an op...   » Read the article

Encyclopedia - Month: Encyclopedia - Month
The month is a unit of time, used with calendars, which is approximately as long as some natural period related to the motion of the Moon...   » Read the article

Encyclopedia - Magnetic Field: Encyclopedia - Magnetic Field
In physics, a magnetic field is an entity produced by moving electric charges (electric currents) that exerts a force on other moving cha...   » Read the article

Encyclopedia - M: Encyclopedia - M
M is the thirteenth letter of the latin alphabet. Its name in English is em. M is also the title of a 1931 film by Fritz Lang, and its 19...   » Read the article

Encyclopedia - Lux: Encyclopedia - Lux
The lux (symbol: lx) is the SI unit of illuminance. It is used in photometry as a measure of the perceived intensity of light. Lux - Defi...   » Read the article

Encyclopedia - Viscosity: Encyclopedia - Viscosity
Viscosity is a measure of the resistance of a fluid to deformation under shear stress. It is commonly perceived as "thickness", or resist...   » Read the article

Encyclopedia - F: Encyclopedia - F
The letter F is the sixth letter in the Latin alphabet. Its name in English is ef, spelled eff when used as a verb. On keyboards, often t...   » Read the article

Encyclopedia - Day: Encyclopedia - Day
A day (symbol: d) is a unit of time equal to 24 hours. It is not an SI unit but it is accepted for use with SI. The SI unit of time is th...   » Read the article

Encyclopedia - C: Encyclopedia - C
C (lowercase c) is the third letter of the Roman alphabet. Its name in English is cee. In the Etruscan language, plosive consonants had n...   » Read the article

Encyclopedia - Barometer: Encyclopedia - Barometer
A barometer is an instrument used to measure atmospheric pressure. Barometer - Liquid barometers. Barometer - Water-based barometers. ...   » Read the article

Encyclopedia - Dimension: Encyclopedia - Dimension
In common usage, the dimensions (from Latin "measured out") of an object are the parameters or measurements required to define its shape ...   » Read the article

Encyclopedia - E: Encyclopedia - E
The letter E is the fifth letter in the Latin alphabet. E - History. E is derived from the Greek letter epsilon which is much the same ...   » Read the article

Encyclopedia - Entropy: Encyclopedia - Entropy
In thermodynamics and statistical mechanics, the thermodynamic entropy (or simply the entropy) S is a key physical variable in describing...   » Read the article

Encyclopedia - Electromagnetic Radiation: Encyclopedia - Electromagnetic Radiation
Electromagnetic radiation is a propagating wave in space with electric and magnetic components. These components oscillate at right angle...   » Read the article

Encyclopedia - Energy: Encyclopedia - Energy
Energy is a measure of being able to do mechanical work.[1] This is a fundamental concept pertaining to the ability for action. In physic...   » Read the article

Encyclopedia - Mass: Encyclopedia - Mass
Mass is a property of physical objects that, roughly speaking, measures the amount of matter they contain. Unlike weight, the mass of som...   » Read the article

Encyclopedia - Omega: Encyclopedia - Omega
Omega (Ω ω) is the 24th and last letter of the Greek alphabet. In the Greek numeric system it had a value of 800. The word literally me...   » Read the article

Encyclopedia - Ammonium Acetate: Encyclopedia - Ammonium Acetate
SI units and standard conditions used unless otherwise stated. Disclaimer and references Ammonium acetate is the salt of ammonia and acet...   » Read the article

Encyclopedia - Ammonium Chloride: Encyclopedia - Ammonium Chloride
General Ammonium chloride Physical Thermochemistry Safety SI units were used where possible. Unless otherwise stated, standard conditio...   » Read the article

Encyclopedia - Admittance: Encyclopedia - Admittance
In electrical engineering, the admittance (Y) is the inverse of the impedance (Z). The SI unit of admittance is the siemens. Oliver Heavi...   » Read the article

Encyclopedia - Volt: Encyclopedia - Volt
The volt (symbol: V) is the SI derived unit of electric potential difference. The number of volts is a measure of the strength of an elec...   » Read the article

Encyclopedia - Atomic Mass Unit: Encyclopedia - Atomic Mass Unit
The unified atomic mass unit (u), or dalton (Da), is a small unit of mass used to express atomic masses and molecular masses. It is defin...   » Read the article

Encyclopedia - Angular Frequency: Encyclopedia - Angular Frequency
In physics (specifically mechanics and electrical engineering), angular frequency ω (also called angular speed) is a scalar measure of r...   » Read the article

Encyclopedia - Angular Acceleration: Encyclopedia - Angular Acceleration
Angular acceleration is the rate of change of angular velocity over time. In SI units, it is measured in radians per second squared (rad/...   » Read the article

Encyclopedia - Angle: Encyclopedia - Angle
An Angle (from the Lat. angulus, a corner, a diminutive, of which the primitive form, angus, does not occur in Latin; cognate are the Lat...   » Read the article

Encyclopedia - Sound Intensity: Encyclopedia - Sound Intensity
The sound intensity, I, (acoustic intensity) is defined as the sound power Pac per unit area A. The usual context is the measurement of s...   » Read the article