Contents

## Fundamental quantities

**These fundamental quantities are considered to be the most basic and cannot be defined in terms of other physical quantities. The choice of fundamental quantities varies depending on the system of units being used. These are independent quantities with units. The dimension of a physical quantity indicates how it is made up in terms of S.I base quantity.**

In other words, the physical quantities is said to have been expressed in terms of fundamental units [Length (L), Mass (M), Time (T), kelvin (k), mole etc].

__Quantity____Dimension__**length L**

**Mass M**

**Time T**

**Kelvin K**

**Mole m**

**Current A**

## Derived quantities

Derived quantities, on the other hand, are quantities that are derived from one or more fundamental quantities through mathematical relationships and equations. These quantities are not considered independent, as their values can be calculated or derived from the values of fundamental quantities. Examples of derived quantities include:

Derived quantity | Derived unit | Dimension |

Area (length x breadth) | m^2 | L^2 |

Volume(length x breadth x height) | m^3 | L^3 |

Density (Mass/volume) | kg/m^3 | M/L/L |

Velocity (Displacement/time) | m/s | L/T |

Acceleration (Velocity/time) | m/s/s | L/T/T |

force (Mass x acceleration | Newton (N) | ML/T/T |

Energy & work (force x distance). | joules | ML^2/T/T |

power (work/time) | joules/s | ML^2/T/T/T |

Momentum (Mass x velocity) | kg m/s | ML/T |

Pressure (force/area) | N/m^2 | ? |

Frequency (no of oscillation/time) | 1/s | 1/T |

## Example

__What is the dimension of EMF?__

EMF(Electromotive Force) is a derived quantity. It is work done by the chemical force to move unit positive charge from negative terminal to positive terminal of the battery.

EMF = Workdone / charge

Work=Force * displacement

=MLT^-2 * L =ML^2T^-2

Charge=Current * time

=IT

Now,

Dimensional formula of

EMF=Work/charge

=ML^2T^-2 / IT

=ML^2T^-3I^-1

**:**

__Exercise__What is the dimension of pressure?