Resonansi terjadi saat reaktansi induktif \(X_L\) sama besar dengan reaktansi kapasitif \(X_C\).
\(X_L = X_C\)
Frekuensi resonansi
\begin{equation*}
\begin{split}
X_L & = X_C \\\\
\omega \:.\: L & = \frac {1}{\omega \:.\: C} \\\\
\omega^2 & = \frac {1}{LC} \\\\
\omega & = \sqrt{\frac {1}{LC}} \\\\
2 \pi \:.\: f & = \frac {1}{\sqrt{LC}} \\\\
f & = \frac {1}{2 \pi \sqrt{LC}}
\end{split}
\end{equation*}
Saat terjadi resonansi, nilai impedanzi \(Z\) mencapai minimum dan kuat arus \(I\) mencapai maksimum.