Technical English & Terminology Course PDF

Technical English & Terminology _ Course What Is a Derived Unit? – Definition and Examples Derived Unit Names and Symbols The names of the derived units are all written using lowercase letters. Most of the names are just combinations of base units, but there are 22 derived units with special name...

Technical English & Terminology _ Course What Is a Derived Unit? – Definition and Examples Derived Unit Names and Symbols The names of the derived units are all written using lowercase letters. Most of the names are just combinations of base units, but there are 22 derived units with special names. The symbols for units named for persons begin with an uppercase letter. Examples of Derived Units For example, the watt, hertz, and coulomb are derived units named for people. Their symbols are W, Hz, and C, respectively. Other examples of derived units include meters per second (m/s), cubic meters (m3), and joule per kelvin (J/K). Med_Amin_DJEDI_Cours_Anglais_Technique_STING_2nd year_Novembre_2023 1  Technical English & Terminology _ Course How Many Derived Units Are There? There are 22 derived units with special names, including the dimensionless derived units the radian (rad) and steradian (sr). However, there are over 100 other derived units that are expressed in terms of their base units. Derived Unit List Here are the 22 derived units with names: Name Symbol Quantity SI Base Units hertz Hz frequency s-1 radian rad angle 1 steradian sr solid angle 1 newton N force kg⋅m⋅s−2 pascal Pa pressure kg⋅m−1⋅s−2 joule J energy kg⋅m2⋅s−2 watt W power kg⋅m2⋅s−3 coulomb C electric charge s⋅A volt V voltage or potential difference kg⋅m2⋅s−3⋅A−1 farad F electrical capacitance kg−1⋅m−2⋅s4⋅A2 ohm Ω electrical resistance kg⋅m2⋅s−3⋅A−2 siemens S electrical conductance kg−1⋅m−2⋅s3⋅A2 weber Wb magnetic flux kg⋅m2⋅s−2⋅A−1 tesla T magnetic flux density kg⋅s−2⋅A−1 Med_Amin_DJEDI_Cours_Anglais_Technique_STING_2nd year_Novembre_2023 2  Technical English & Terminology _ Course henry H electrical inductance kg⋅m2⋅s−2⋅A−2 degree °C temperature relative to 273.15 K K Celsius lumen lm luminous flux cd lux lx illuminance cd⋅m−2 becquerel Bq radioactive decays per unit time s−1 gray Gy absorbed dose of ionizing radiation m2⋅s−2 sievert Sv equivalent dose of ionizing radiation s−1⋅mol katal kat catalytic activity s−1⋅mol Derived Units and Dimensional Analysis Many other derived units are mathematical combinations of SI base units, just without special names. Here are some examples: Quantity Symbol Unit Abbreviation Derivation area A square meter m2 length x width volume V cubic meter m3 length x width x height density ρ kilograms per cubic meter kg/m3 mass / volume concentration c or M moles per liter mol/L amount / volume (molarity) speed v meters per second m/s length / time Med_Amin_DJEDI_Cours_Anglais_Technique_STING_2nd year_Novembre_2023 3  Technical English & Terminology _ Course Quantity Symbol Unit Abbreviation Derivation acceleration a meters per second per second m/s2 speed / time angular rad/s radians per second rad/s angle / time velocity current A/m2 ampere per square meter A/m2 current / time density wave number m-1 reciprocal meter m-1 1 / length specific ν cubic meter per kilogram m3/kg volume / mass volume Who Can Make a Derived Unit? There are so many derived units that you might think anyone could make one up, providing they use the base units as a starting point. But, a unit only comes into being if it is published in The International System of Units (SI). The General Conference on Weights and Measures (CGPM) manages the International System of Units (SI or metric system) and makes recommendations to the International Committee for Weights and Measures (CIPM). The International Bureau of Weights and Measures (BIPM) periodically reports updates to the unit list and definitions. Non-SI Units The metric system also includes several units which are neither base units nor derived units. These units exist within the metric system either because they are multiples or fractions of SI units or else they are practical. The permitted non-SI units are: Med_Amin_DJEDI_Cours_Anglais_Technique_STING_2nd year_Novembre_2023 4  Technical English & Terminology _ Course Name Symbol Quantity minute min time hour h time day d time astronomical unit au length degree ° plane angle minute ′ plane angle second ″ plane angle hectare ha area liter or litre l volume tonne t mass dalton Da mass electronvolt eV energy neper Np logarithmic ratio bel, decibel B, dB logarithmic ratio Med_Amin_DJEDI_Cours_Anglais_Technique_STING_2nd year_Novembre_2023 5  Technical English & Terminology _ Course Several permitted units in the 8th SI brochure did not make it into the 9th brochure. Among these are the bar (pressure), mmHg (pressure), ångström (length), and gauss (magnetic flux density). References  Atkins, Tony; Escudier, Marcel (2019). A Dictionary of Mechanical Engineering. Oxford University Press. ISBN 9780199587438.  International Bureau of Weights and Measures (2006). The International System of Units (SI) (8th ed.). ISBN 92-822-2213-6.  Bureau International des Poids et Mesures (2019). The International System of Units (SI) (9th ed.).  Mills, I.; Cvitas, Tomislav; Homann, Klaus; Kallay, Nikola (1993). Quantities, Units and Symbols in Physical Chemistry (2nd ed.). Blackwell Science Inc. Med_Amin_DJEDI_Cours_Anglais_Technique_STING_2nd year_Novembre_2023 6  Technical English & Terminology _ Course SI Base Units The SI base units are standard units of measurement in the International System of Units (SI) for seven base quantities. All other SI units are derived from this simple set of seven units. Here is a list of the SI base units, their abbreviations, and a look at their current and past definition. The Seven SI Base Units Here are the seven SI base units and their abbreviations: Med_Amin_DJEDI_Cours_Anglais_Technique_STING_2nd year_Novembre_2023 7  Technical English & Terminology _ Course Unit Symbol Measure second s time meter or metre m length kilogram kg mass ampere A electric current kelvin K thermodynamic temperature mole mol amount of substance candela cd luminous intensity Note that the names of all of the SI base units are written in lowercase letters, even when they honor a person. The symbols, however, are lowercase letters except when they honor a person. So, the symbol for the kelvin is K because it takes its name from Lord Kelvin and the ampere has the symbol A because it is named for André-Marie Ampère. SI Unit Definitions – Past and Present On May 20, 2019, the International Bureau of Weights and Measures (BIPM) officially re-defined the seven base units. The reason is so all of the base unit definitions come from a property of nature (which remain constant) and not some physical object (which could change over time). Med_Amin_DJEDI_Cours_Anglais_Technique_STING_2nd year_Novembre_2023 8  Technical English & Terminology _ Course  Second: The second is based on an atomic clock. It is the duration of 9,192,631,770 periods of transition between the two hyperfine levels of the ground state of the caesium-133 atom at 0 K. Previously, the was defined according to the mean solar day of 24 hours, where each hour has 60 minutes and each minute has 60 seconds. In other words, the second was defined as 1⁄86400 of one day. As it turns out, each day isn’t the same length, so the original definition wasn’t as constant as you might think.  Meter: The meter (or metre, depending where you live) depends on the definition of the second and the speed of light in a vacuum, which is a constant. The meter is the distance travelled by light in a vacuum in 1/299792458 of a second. The original meter definition in 1793 was one ten-millionth of the distance from the equator to the North Pole, travelling along a great circle. Since the Earth isn’t actually round, much less smooth, the definition wasn’t the best. Later, the definition depended on a prototype meter bar and then on a number of wavelengths of an emission line of the noble gas krypton-86.  Kilogram: The modern kilogram definition depends on Planck’s constant, the meter definition, and the second definition. It is the mass from Planck’s constant h, when expressed in the units kg m2 s-1, where the meter and second are defined and Planck’s constant is fixed at 6.62607015×10−34 J s or kg m2 s-1. The original kilogram definition was the mass of one liter of water at the melting point of water, which was liter was one thousandth of a cubic meter.  Ampere: The ampere definition depends on the charge of the electron. The electron charge is a fixed value of 1.602176634×10−19 C, where a coulomb C is an ampere second A s. The original definition was the electrical current required to deposit 1.118 milligrams of silver per second from silver nitrate. Later, the definition changed such that it was the constant current between two parallel conductors one meter apart in a vacuum that produced a force of 2 x 10 - 7 newton’s per meter. Med_Amin_DJEDI_Cours_Anglais_Technique_STING_2nd year_Novembre_2023 9  Technical English & Terminology _ Course  Kelvin: The kelvin definition depends on the Boltzmann constant and the definitions of the meter, kilogram, and second. It is the temperature obtained when the Boltzmann constant k is expressed in J K-1, which is the same as kg m2 s-2 K- 1. The Boltzmann constant is 1.380649×10−23 J/K. Originally, the kelvin was temperature using the same size increment as the Celsius degree, but starting at absolute zero.  Mole: The mole depends on the definition of Avogadro’s constant, which is exactly 6.022 140 76 × 1023 particles. Avogadro’s number is the value of Avogadro’s constant expressed in the mol-1 unit. The earlier definition depended on an empirical measurement of the number of atoms in 0.012 kilograms of the isotope carbon-12.  Candela: The candela depends on the light emitted by a green light of a specified power and the kilogram, meter, and second definitions. The illumination from monochromatic light with a frequency of 540 × 1012 Hz (about 555 nm) is 683 lm W-1, which is the same unit as cd sr kg-1 m-2 s3. The original candela unit comes from the candlepower, which is the light emitted by a burned candle under standard conditions. References  Bureau International des Poids et Mesures (2019). The International System of Units (SI) (9th ed.). 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