SI system

The CGS, MKS and FPS systems used only three fundamental quantities (mass, length and time) for the measurement of a physical quantity. However, these three fundamental quantities were found insufficient to measure some physical quantities in thermodynamics, optics and current electricity. For example, the amount of current in a circuit could not be expressed in terms of mass, length and time. To solve the problem, another system of unit called SI(System International de Units) units came into existence. In fact, the international convention of scientists held in France in 1968 decided to use the SI units. In addition to mass, length and time as the fundamental quantities, the SI units added a few more quantities as the fundamental quantities. They are temperature, electric current, luminous intensity and amount of substances.