Units and Measurement
(i). Physics is a quantitative science, based on measurement of physical quantities. Certain physical quantities have been chosen as fundamental or base quantities (such as length, mass, time, electric current, thermodynamic temperature, amount of substance, and luminous intensity).
(ii). Each base quantity is defined in terms of a certain basic, arbitrarily chosen but properly standardized reference standard called unit (such as meter, kilogram, second, ampere, kelvin, mole and candela). The units for the fundamental or base quantities are called fundamental or base units.
(iii). Other physical quantities, derived from the base quantities, can be expressed as a combination of the base units and are called derived units. A complete set of units, both fundamental and derived, is called a system of units.
(iv). The International System of Units (SI) based on seven base units is at present internationally
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