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Thus, for example, the CGS unit of pressure, barye, is related to the CGS base units of length, mass, and time in the same way as the SI unit of pressure, pascal, is related to the SI base units of length, mass, and time: 1 unit of pressure = 1 unit of force / (1 unit of length) 2 = 1 unit of mass / (1 unit of length × (1 unit of time) 2)
One difference between the Gaussian and SI systems is in the factor 4π in various formulas that relate the quantities that they define. With SI electromagnetic units, called rationalized, [3] [4] Maxwell's equations have no explicit factors of 4π in the formulae, whereas the inverse-square force laws – Coulomb's law and the Biot–Savart law – do have a factor of 4π attached to the r 2.
The unit of momentum is the product of the units of mass and velocity. In SI units, if the mass is in kilograms and the velocity is in meters per second then the momentum is in kilogram meters per second (kg⋅m/s).
Giorgi later identified the need for an electrical base unit, for which the unit of electric current was chosen for SI. Another three base units (for temperature, amount of substance, and luminous intensity) were added later. [1] The early metric systems defined a unit of weight as a base unit, while the SI defines an analogous unit of mass.
Polarizability has the SI units of C·m 2 ·V −1 = A 2 ·s 4 ·kg −1 while its cgs unit is cm 3. Usually it is expressed in cgs units as a so-called polarizability volume, sometimes expressed in Å 3 = 10 −24 cm 3. One can convert from SI units to cgs units (′) as follows:
Typical dipole moments for simple diatomic molecules are in the range of 0 to 11 D. Molecules with symmetry point groups or containing inversion symmetry will not have a permanent dipole moment, while highly ionic molecular species have a very large dipole moment, e.g. gas-phase potassium bromide, KBr, with a dipole moment of 10.41 D. [3] A proton and an electron 1 Å apart have a dipole ...
Forms of matter that are not composed of molecules and are organized by different forces can also be considered different states of matter. Superfluids (like Fermionic condensate) and the quark–gluon plasma are examples. In a chemical equation, the state of matter of the chemicals may be shown as (s) for solid, (l) for liquid, and (g) for gas.
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 ...