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} = [L^{3}]

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 [M
^{0}].

Dimensions do not take into account the magnitude of a quantity

.