What is the difference between derived units and base units

Return to Units home page. Units Topics:. Units Bibliography. SI base units The SI is founded on seven SI base units for seven base quantities assumed to be mutually independent, as given in Table 1.

SI base units. Examples are mass and electric charge. A quantity in the particular sense is a quantifiable or assignable property ascribed to a particular phenomenon, body, or substance. Examples are the mass of the moon and the electric charge of the proton. In , in world confidence, a consensus evolved, and a standard international system of units. Standards of Length The most common unit is the meter m , Foot is also used sometimes. In the standard meter was defined as the distance between two fixed marks engraved on a platinum-iridium bar preserved at a constant temperature of All other meters are calibrated with it to an accuracy of 0.

In the standard meter was defined in terms of the wavelength of Kr and is called the atomic standard of length.

An accuracy 9 parts can be obtained with it. It can be reduced to its elementary level as kg. Expressing derived unit in terms of fundamental unit: Since fundamental units are elementary in nature and cannot be reduced further, so it cannot be expressed in terms of other units.

On the other hand, derived units can be reduced to its elementary level and thus it can be expressed in terms of fundamental units. For example, unit of mechanical work is Joule J , which is one derived unit.

Since every derived unit can be expressed in terms of fundamental units, so Joule can also be written as N. In conclusion it can be said that derived unit can be expressed by fundamental units, but not vice versa. Number of such units present in Metric System: There exist only seven fundamental units in SI system, which are meter unit of length , kilogram unit of mass , second unit of time , kelvin unit of temperature , mole unit for amount of substance , ampere unit of current , and candela unit of luminous intensity.

There exist a large number of derived units in SI system. Thus entire Metric System is composed of seven fundamental units and ample derived units.

Skip to content.