= Electrical reference potential
{title2=$\Phi_{\mathrm{ref}}=0$}
An <electrical reference potential> fixes the arbitrary additive constant of an <electric potential>. Assigning zero to ground makes other potentials differences from that baseline; it does not assert that the <electric field> vanishes there. If a source calculation gives $\Phi(a)=89.9\,\mathrm V$ and $\Phi(b)=179.8\,\mathrm V$ relative to infinity, choosing $a$ as the zero instead gives $\Phi'(a)=0$ and $\Phi'(b)=89.9\,\mathrm V$, with the same <electric potential difference>. Grounding an <electrical conductor> additionally connects it to a reservoir that can exchange <electric charge> to maintain the prescribed <electric potential>; that physical boundary condition differs from merely relabeling an unchanged solution.<University Physics Volume 2 by Samuel J. Ling and others/7.3 Calculations of Electric Potential>[§7.3: potential references, including ground in Figure 7.18]{ref}; https://www.feynmanlectures.caltech.edu/II_06.html#Ch6-S8[Feynman lectures II.6, §6–8: a grounded conducting plane]{ref}.
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