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# What is the difference between fundamental quantity and dimension?

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## Fundamental quantities are those physical quantities that cannot be expressed in terms other quantities. It is independent on its own. For example: Mass, Length, time, temperature, electric current Dimension, in physics, of a physical quantity is the index of each of the fundamental quantity ( Length, mass, time, temperature, Luminous intensity, Current ) which expresses that quantity. For example, the dimension of speed can be derived in the following way: Speed= distance/time = length/time = L/T = L.T^-1. The above expression tells you the dimension of "speed". In its dimension, there is no mention of mass, current or temperature because they don't play any role in defining this quantity. Or, you could say the dimension of mass in this expression is zero, that of current , luminous intensity, temp too is zero. In a completely different sense, dimension is about the space an object takes up. It signifies length, breadth, and height/thickness of the physical object which occupies space. So the dimensions of a brick could be expressed as 20cm*10cm*6cm Fundamental quantities 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

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