Class 11 Physics Units and Measurements Dimensions of a Physical Quantity

Dimensions of a Physical Quantity

Dimensions of a physical quantity are powers (exponents) to which base quantities are raised to represent that quantity. They are represented by square brackets around the quantity.

  • Dimensions of the 7 base quantities are – Length [L], Mass [M], time [T], electric current [A], thermodynamic temperature [K], luminous intensity [cd] and amount of substance [mol].

Examples, Volume = Length x Breadth x Height = [L] x [L] x [L] = [L]3 = [L3]

Force = Mass x Acceleration = [M][L]/[T]2 = [MLT-2]

  • The other dimensions for a quantity are always 0. For example, for volume only length has 3 dimensions but the mass, time etc have 0 dimensions. Zero dimension is represented by superscript 0 like [M0].

Dimensions do not take into account the magnitude of a quantity

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