119Fundamental quantites are terms used very often. Ampere is a very common term and so it is called a fundamental unit.
I think so.
ampere=charge/time
A=q/t
so why do we call it a fundamental unit? charge should have been the fundamental unit like time.
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3 Answers
49Let us consider this simple equation:
v = L/t
Since, L and t are fundamental quantities, from the above equation we can happily conclude that v is a derived quantity.
So far so good.
No we try to do some simple mathematical manipulations with the above simple equation. The same equation can be re-written as:
L= v*t
Now, we have a problem. L (length) which was initially considered to be a fundamental quantity (since it could not be expressed in terms of any other physical quantity) has been expressed in terms of two other physical quantity. Thus, can we really say that L is a fundamental quantity?
Similarly, when we write t = v/L, can we say that t is a fundamental quantity? (If you notice, I just expressed t in terms of two other physical quantities.)
Thus, we should pose a question. Why are certain quantities fundamental and the others derived?
Length, time, mass etc. are fundamental just because we have defined them to be fundamental. We could have very easily called velocity to be a fundamental quantity instead of Length or time.
There were certain physical quantities that the early physicists 'liked'. They called them fundamental quantities. And others, obviously following the relations, became derived.
I hope now everything became clear.
5My best guess would be, that current was considered a fundamental quantity before charge.
Your equation can be rewritten as:
q=A*t
this means, if current and time are fundamental, charge is derived.
It's all relative. Hope this helps.
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