= Parallel-plate transmission line
{title2=$C'=\varepsilon a/d,\quad L'=\mu_0d/a$}
Two perfectly conducting wide strips of width $a$ and separation $d\ll a$, filled with a homogeneous nonmagnetic <dielectric> of absolute <permittivity> $\varepsilon$, support a <transverse electromagnetic mode>. Ignoring edge fields, their distributed <capacitance> is $C'=\varepsilon a/d$ and distributed external <inductance> is $L'=\mu_0d/a$. The magnetic-energy integral $\mu_0(I/a)^2ad/2=L'I^2/2$ gives the latter. Their <characteristic impedance> is $Z_0=(d/a)\sqrt{\mu_0/\varepsilon}$ and propagation speed is $1/\sqrt{\mu_0\varepsilon}$. These parameters are per unit length, distinct from a lumped capacitor and inductor.
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