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Dimensions

All the physical quantities represented by derived units can be expressed in terms of some combination of seven fundamental quantities. These seven fundamental quantities are called seven dimensions of the physical world. They are denoted with square brackets [ ].

The dimensions of a physical quantity are the powers (or exponents) to which the base quantities are raised to represent that quantity. Note that
• In this type of representation the magnitudes are not considered. It is the quality of the type of the physical quantity that enters.
• The expression which shows how and which of the base quantities represent the dimensions of a physical quantity is called dimensional formula of the given physical quantity.
• The equation obtained by equating a physical quantity with its dimensional formula is called dimensional equation of the physical quantity. For example,

[S] = [M 0L2T â€“2K â€“1]               (i)