In Class 11 Physics (Units and Measurements), you learn that all physical quantities can be expressed in terms of basic fundamental dimensions like Mass [M], Length [L], Time [T], and Electric Current [A].
The SI unit of electric charge is the Coulomb (C).
From the formula, we can see that 1 Coulomb is exactly equal to 1 Ampere-second.
The charge of a single electron is approximately $-1.6 \times 10^{-19}$ Coulombs.
Electric charge (Q) is not considered a fundamental physical quantity in the SI system. Instead, Electric Current (I) is considered the fundamental quantity.
The basic formula relating charge and current is: Electric Current (I) = $\frac{\text{Charge (Q)}}{\text{Time (t)}}$
Therefore, rearranging the formula gives: Charge (Q) = Current (I) $\times$ Time (t)
To find the dimension of charge, we plug in the fundamental dimensions of Current and Time:
So, Dimension of Q = $[A] \times [T]$ = $[AT]$.
Written in the standard complete format showing Mass and Length as zero, the dimensional formula of electric charge is:
$[M^0 L^0 T^1 A^1]$
It is purely a historical and practical convention. Electric current (Ampere) was much easier to measure accurately in early laboratories using magnetic forces than static electric charge was.
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