= Equal-ratio RC bridge
{title2=$\omega_0^{-2}=R_x^2C_x(C-C_x)$}
A bridge driven between top and bottom nodes has equal <resistors> on its left arms, upper-right <electrical impedance> $Z=R_x/(1+i\omega R_xC_x)$ and lower-right <electrical impedance> $W=R_v+1/(i\omega C)$. A zero detector <electric current> requires $Z=W$. Equating <real parts> and <imaginary parts> gives $R_v=R_x(1-C_x/C)$ and $\omega_0^{-2}=R_x^2C_x(C-C_x)$, requiring $0<C_x<C$. Its open-circuit right-minus-left junction <voltage> is $V_0(W-Z)/[2(W+Z)]$, whereas a connected ideal <ammeter> has zero terminal <voltage> at every <angular frequency>. This distinction separates a null-current measurement from an unloaded voltage measurement.
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