By using Coulomb’s law, define unit charge.
By using Coulomb’s law, define unit charge.
In $SI$, the unit of charge is Coulomb.
Putting value of $q_{1}=q_{2}=1 \mathrm{C}, r=1 \mathrm{~m}$ in $\mathrm{F}=k \frac{q_{1} q_{2}}{r^{2}}$, then $\mathrm{F}=\frac{1}{4 \pi \epsilon_{0}}=9 \times 10^{9} \mathrm{~N}$
Definition of $1 \mathrm{C}: 1 \mathrm{C}$ is the charge that when placed at a distance of $1 \mathrm{~m}$ from another charge of the same magnitude in vacuum experiences an electrical force of repulsion of magnitude $9 \times 10^{9} \mathrm{~N}$.
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