Coulomb law
Coulomb law is fundamental scientific concept about interaction of electric charges.
The special conserving quantity is postulated, called electric charge.
Potential energy of interaction of two charges $q_1$ and $d_2$ localised in regions small compared to the distance $r$ between them, is postulated to be
$\displaystyle U=k \frac{q_1 q_2}{r}$
where $k$ is fundamental constant determined by unit of measurement of the electric charge.
In the system SI, unit of charge is Coulomb, and
$\displaystyle k=\frac{1}{4 \pi \varepsilon_0} \approx 8.9875517873681764\times 10^9 \mathrm{Newton\, Meter^2\, Coulomb}^{-2} $
Do physicians know physics?
Since century 20, the popular questions for students of medical institutes was: How many physicians know physics?
The similar question refer to Mathematica with respect to the example below:
Needs["PhysicalConstants`"] VacuumPermittivity N[VacuumPermittivity] ElectronCharge ElectronCharge^2/(4 Pi VacuumPermittivity )
The last line produces output $\mathrm{ (2.30708\times 10^{-28} Coulomb^2~ Meter~ Volt)/(Ampere~ Second) }$
instead of expected
$\mathrm{ 2.30708\times 10^{-28}~ Joule~ Meter }$
References
https://en.wikipedia.org/wiki/Coulomb%27s_law
