Appendix-B
The International System of Units (SI)
Table 1 The SI Base Units| Quantity | Name | Symbol | Definition |
|---|---|---|---|
| length | meter | m | “. . . the length of the path traveled by light in vacuum in 1/299,792,458 of a second.” (1983) |
| mass | kilogram | kg | “. . . this prototype [a certain platinum–iridium cylinder] shall henceforth be considered to be the unit of mass.” (1889) |
| time | second | s | “. . . the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom.” (1967) |
| electric current | ampere | A | “. . . that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross section, and placed 1 meter apart in vacuum,would produce between these conductors a force equal to \(2\times10^{-7}\) newton per meter of length.” (1946) |
| thermodynamic temperature | kelvin | K | “. . . the fraction 1/273.16 of the thermodynamic temperature of the triple point of water.” (1967) |
| amount of substance | mole | mol | “. . . the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon-12.” (1971) |
| Quantity | Name of Unit | Symbol |
|---|---|---|
| area | square meter | \(m^2\) |
| volume | cubic meter | \(m^3\) |
| fequency | hertz | Hz \((s^{-1})\) |
| mass density (density) | kilogram per cubic meter | \(kg/m^3\) |
| speed, velocity | meter per second | m/s |
| angular velocity | radian per second | rad/s |
| acceleration | meter per second per second | \(m/s^2\) |
| angular acceleration | radian per second per second | \(rad/s^2\) |
| force | newton | N (kg.m/s^2) |
| pressure | pascal | \(Pa (N/m^2)\) |
| work, energy, quantity of heat | joule | J (N.m) |
| power | watt | W (J/s) |
| quantity of electric charge | coulomb | C (A.s) |
| potential difference, electromotive force | volt | V (W/A) |
| electric field strength | volt per meter (or newton per coulomb) | V/m (N/C) |
| electric resistance | ohm | \(\Omega (V/A)\) |
| capacitance | farad | F (A.s/V) |
| magnetic flux | weber | Wb (V.s) |
| inductance | henry | H (V.s/A) |
| magnetic flux density | tesla | T \((Wb/m^2)\) |
| magnetic field strength | ampere per meter | A/m |
| entropy | joule per kelvin | J/K |
| specific heat | joule per kilogram kelvin | J/(kg.K) |
| thermal conductivity | watt per meter kelvin | |
| radiant intensity | watt per steradian | W/sr |