Grounded-plate potential of a central charged sheet ($V_{\mathrm{sheet}}=\sigma d/(4{ϵ}_0)$)

An ideal infinite sheet midway between parallel grounded plates has equal fields of magnitude $\sigma /(2{ϵ}_0)$ on its two sides, directed from positive sheet charge toward the plates. Integrating over the half-separation d/2 gives the displayed electric potential. Each plate carries induced inner-face surface charge density $-\sigma /2$. The potential is triangular between the plates, and the field jumps by $\sigma /{ϵ}_0$ across the sheet. Edge fields are excluded.