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 $9 \times 10^{9} \mathrm{~N}$.
$12$ positive charges of magnitude $q$ are placed on a circle of radius $R$ in a manner that they are equally spaced. A charge $Q$ is placed at the centre, if one of the charges $q$ is removed, then the force on $Q$ is
An electron is moving round the nucleus of a hydrogen atom in a circular orbit of radius $r$. The coulomb force $\overrightarrow F $ between the two is (Where $K = \frac{1}{{4\pi {\varepsilon _0}}}$)
If $g_E$ and $g_M$ are the accelerations due to gravity on the surfaces of the earth and the moon respectively and if Millikan's oil drop experiment could be performed on the two surfaces, one will find the ratio (electronic charge on the moon/electronic charge on the earth) to be
A charge $q$ is placed at the centre of the line joining two equal charges $Q$. The system of the three charges will be in equilibrium, if $q$ is equal to
Two charges each equal to $2\,\mu C$ are $0.5\,m$ apart. If both of them exist inside vacuum, then the force between them is.......$N$