# 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)
Table 2 Some SI Derived Units W/(m.K)
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
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 $$\Omega (V/A)$$
magnetic flux density tesla T $$(Wb/m^2)$$