Question
State the formula of an electric current and define its unit.

Answer

If a net amount of electric charge $Q$, flows across any cross-section of a conductor in time $t$, then the current $I$, through the crosssection is
$
I=\frac{Q}{t}
... ...(11.1)$
$\rightarrow$ SI unit of electric charge is coulomb (C) and time is second (s).
$\rightarrow$ The SI unit of electric current is ampere (A), named after the French scientist, Andre-Marie Ampere.
$\rightarrow$ Hence from equation (11.1), $A=\frac{C}{s}$
Definition of ampere (A) : If 1 coulomb charge flows through any cross-section of a conductor in 1 second, then the electric current flowing through the conductor is said to be 1 ampere.
$
\text { i.e., } 1 A=\frac{1 C}{1 s}=1 C s^{-1}
$

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