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Encyclopedia of Electrical Engineering realnfo.com
Encyclopedia of Electrical Engineering

# Physical Quantities

A physical quantity is a quantity which can be measured. For example length, weight, volume etc are physical quantity. By using these physical quantities we can find some basic attributes of an object.

#### Fundamental Quantities

Those quantities which do not depend on other quantities are the fundamental quantities. There are seven fundamental quantities. These are Length, Mass, Time, Electric Current, Temperature, Luminous Intensity and Amount of Matter.

#### Derived Quantities

Those quantities which are dependent on fundamental quantities are termed as derived quantities. Examples of derived quantities are Area, Volume, Speed, Force, Work etc. Fig.no.1: Fundamental Quantities with units and symbols. Fig.no.2: Derived Quantities with units and symbols.

#### Scalar Quantities

A physical quantity which can be expressed only by magnitude (By a numerical value) is known as scalar quantity. Mass, Time, Temperature, Speed, work are scalar quantities.

#### Vector Quantities

Those quantities which need both magnitude and direction to express the quantity completely and also follow the laws of vector algebra are the Vectors. Figure no.3: Scalar Quantities Fig.no.4: Difference between scalar and vector