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James Clerk Maxwell played a major role in developing the concept of a coherent CGS system and in extending the metric system to include electrical units.. A coherent system of units is a system of units of measurement used to express physical quantities that are defined in such a way that the equations relating the numerical values expressed in the units of the system have exactly the same ...
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 names of SI ...
For example, 1 m/s = (1 m) / (1 s) is the coherent derived unit for velocity. [1]: 139 With the exception of the kilogram (for which the prefix kilo- is required for a coherent unit), when prefixes are used with the coherent SI units, the resulting units are no longer coherent, because the prefix introduces a numerical factor other than one.
The units of the first two quantities are the ampere and the ampere per centimetre respectively. The unit of magnetic permeability is that of the emu system, and the magnetic constitutive equations are B = (4 π /10)μH and B = (4 π /10)μ 0 H + μ 0 M. Magnetic reluctance is given a hybrid unit to ensure the validity of Ohm's law for magnetic ...
Units of logarithmic frequency ratio include the octave, corresponding to a factor of 2 in frequency (precisely) and the decade, corresponding to a factor 10. The ISQ recognizes another logarithmic quantity, information entropy, for which the coherent unit is the natural unit of information (symbol nat). [citation needed]
The oersted (/ ˈ ɜːr s t ɛ d /,; [1] symbol Oe) is the coherent derived unit of the auxiliary magnetic field H in the centimetre–gram–second system of units (CGS). [2] It is equivalent to 1 dyne per maxwell.
In partial differential equation form and a coherent system of units, ... ∂ α is the partial derivative with respect to the coordinate, x ...
While a base unit is one that has been explicitly so designated, [2] a derived unit is unit for a derived quantity, involving the combination of quantities with different units; [1] several SI derived units are specially named. A coherent derived unit involves no conversion factors.