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The SI has special names for 22 of these coherent derived units (for example, hertz, the SI unit of measurement of frequency), but the rest merely reflect their derivation: for example, the square metre (m 2), the SI derived unit of area; and the kilogram per cubic metre (kg/m 3 or kg⋅m −3), the SI derived unit of density.
The kelvin is defined by setting the fixed numerical value of the Boltzmann constant k to 1.380 649 × 10 −23 J⋅K −1, (J = kg⋅m 2 ⋅s −2), given the definition of the kilogram, the metre, and the second.
kg⋅m 2 ⋅s –2 ⋅A –2: L, M inductance: henry: H = Wb/A = V⋅s/A kg⋅m 2 ⋅s −2 ⋅A −2: μ permeability: henry per metre: H/m kg⋅m ⋅s −2 ⋅A −2: χ magnetic susceptibility (dimensionless) 1 1 m magnetic dipole moment: ampere square meter: A⋅m 2 = J⋅T −1: A⋅m 2: σ mass magnetization: ampere square meter per ...
m 3 ⋅kg −1: L 3 M −1: intensive Spin: S: Quantum-mechanically defined angular momentum of a particle kg⋅m 2 ⋅s −1: L 2 M T −1: Strain: ε: Extension per unit length unitless 1: Stress: σ: Force per unit oriented surface area Pa L −1 M T −2: order 2 tensor Surface tension: γ: Energy change per unit change in surface area N/m ...
The SI comprises a coherent system of units of measurement starting with seven base units, which are the second (symbol s, the unit of time), metre (m, length), kilogram (kg, mass), ampere (A, electric current), kelvin (K, thermodynamic temperature), mole (mol, amount of substance), and candela (cd, luminous intensity).
For example, the CGS unit of force is the dyne, which is defined as 1 g⋅cm/s 2, so the SI unit of force, the newton (1 kg⋅m/s 2), is equal to 100 000 dynes. On the other hand, in measurements of electromagnetic phenomena (involving units of charge , electric and magnetic fields, voltage , and so on), converting between CGS and SI is less ...
The pascal (Pa) or kilopascal (kPa) as a unit of pressure measurement is widely used throughout the world and has largely replaced the pounds per square inch (psi) unit, except in some countries that still use the imperial measurement system or the US customary system, including the United States.
High Definition Television, any television system with more than 625 scan lines. headphone An audio transducer or pair of transducers arranged to be worn on (or in) the ear. heat transfer The study of the flow of heat energy; heat transfer concerns dictate major design features of most electrical and electronic systems. heatsink