= von Klitzing constant
{c}
{title2=$R_K=h/e^2$}
The <von Klitzing constant> is $R_K=h/e^2=25812.807459\ldots\,\Omega$. The current <SI> fixes the <Planck constant> $h=6.62607015\times10^{-34}\,\mathrm{J\,s}$ and <elementary charge> $e=1.602176634\times10^{-19}\,\mathrm C$ exactly, so $R_K$ is exact; the displayed decimal is truncated. It differs from the historical conventional value $R_{K\text{-}90}=25812.807\,\Omega$.<Fundamental Physical Constants — Complete Listing by National Institute of Standards and Technology and others>[2022 CODATA adjustment: Planck constant, elementary charge, von Klitzing constant and conventional-value rows]{ref}
As an original ideal example, $N=2$ and <electric current> $I=1\,\mu\mathrm A$ give $|V_H|=IR_K/2\simeq12.9064\,\mathrm{mV}$. Changing the <Hall bar>'s width changes the transverse <electric field> required for this <electric potential difference>, while the ideal ratio $|V_H|/I$ remains $R_K/2$.
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