Gordon England Surface Engineering Forum

Natural and atomic units

In some cases, the values of quantities are expressed in terms of fundamental constants of nature or so-called natural units. The use of these units occur when it is necessary for the most effective communication of information. In such cases, the specific natural units that are used must be identified. Examples of some physical quantities used as natural units are given in the table. While theoretical results intended primarily for other theorists may be left in natural units, if they are also intended generally, they must also be given in acceptable units.

Some Fundamental Physical Constants

Physical Quantity
Symbol
Value in SI Units
speed of light in vacuumc, co299 792 458 m s-1
elementary chargee1.602 176 53(14) x 10-19 C
Planck constanth6.626 0693(11) x 10-34 J s
Avogadro constantL, NA6.022 1415(10) x 1023 mol-1
electron massme9.109 3826(16) x 10-31 kg
proton massmp1.672 621 71(29) x 10-27 kg
electronvolteV1.602 176 53(14) x 10-19 J
Faraday constantF9.648 533 83(83) x 104 C mol-1
Hartree energyEh4.359 744 17(75) x 10-18 J
Bohr radiusao5.291 772 108(18) x 10-11 m
Bohr magnetonµB9.274 009 49(80) x 10-24 J T-1
nuclear magnetonµN5.050 783 43(43) x 10-27 J T-1
Rydberg constantR10 973 731.568 527(73) m-1
molar gas constantR8.314 472(15) J mol-1 K-1
Boltzmann constantk, kB1.380 650 5(24) x 10-23 J K-1
gravitational constantG6.6742(10) x 10-11 m3 kg-1 s-2
standard acceleration of gravitygn 9.806 65 m s-2
triple point of waterTtp(H20)273.16 K
zero of Celsius scaleT(0oC)273.15 K
molar volume of ideal gas
(273.15 K, 100 kPa)
Vm 22.710 981(40) x 10-3 m3 mol-1
magnetic constant
(permeability of vacuum)
µo 4p x 10-7 =
12.566 370 614 x 10-7 N A-2
electric constant
(permittivity of vacuum)
eo 8.854 187 817 x 10-12 F m-1
Table 10. Some Fundamental Physical Constants.

Si Units:
SI Base Units
SI Derived Units
expressed with special names
expressed in terms of SI base units
expressed in terms in terms of SI units with special names
SI Unit Prefixes
Non-SI Units
accepted by SI
currently accepted by SI
derived CGS units with special names
other non-SI units
Constants
Glossary of Units






CONVERSION CALCULATORS

Convert between Different Units of Measurement

Index of Unit Converters
ACCELERATION
ANGLE
AREA
AREA
DENSITY
DENSITY
DISTANCE
DYNAMIC
VISCOSITY
ENERGY
ENERGY
DENSITY
ENTROPY
FEED RATE
FLOW RATE
FORCE
FUEL
CONSUMPTION
HEAT
CAPACITY
HEAT FLUX
DENSITY
HEAT TRANSFER
COEFFICIENT
IRRADIANCE
KINEMATIC
VISCOSITY
LENGTH
MASS
POWER
PRESSURE
SPECIFIC
ENERGY
SPECIFIC
ENTHALPY
SPECIFIC
ENTROPY
SPECIFIC HEAT
CAPACITY
SPECIFIC
VOLUME
SPEED
TEMPERATURE
THERMAL
CONDUCTIVITY
TIME
TORQUE
VELOCITY
VOLUME
VOLUMETRIC
HEAT CAPACITY
Unit Prefixes
Plasma
Gas Flow
Hardness
MPa - GPa
Computing
Bits and Bytes

To use the measurement conversion calculators simply enter a number value into the desired field and click calculate. All results shown will be equivalent values. Values are given to seven significant figures ( the odd result may show 9's or 0's over running). Values of 10 000 or greater will be displayed in the e-format e.g. 2.3456e7 which equals 2.3456 x 107 or 23 456 000. Values lower than 0.001 will be displayed in the e-format e.g. 2.3456e-5 which equals 2.3456 x 10-5 or 0.000 023456. The calculators require that your browser has java script enabled. View all measurement unit conversion calculators on the same page (may not work with all browsers; requires Iframe).



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