English: Animated diagram showing the operation of a tuned circuit (LC circuit). This is an improvement over previous versions of this animation which uses variable frame display times to show a more realistic movement of the charge.

A tuned circuit is a very simple electronic circuit widely used in audio, radio and television equipment. It consists of an inductor L (coil of wire, left) and a capacitor C (right) connected together. Tuned circuits can store electrical energy oscillating at its resonant frequency. The capacitor stores energy in its electric field E and the inductor stores energy in its magnetic field B (green). When the capacitor is charged with electricity and connected to the coil, the charge flows back and forth between the capacitor's plates as a current i (red) through the coil as shown. This jerky animation shows "snapshots" of the circuit at progressive points in the oscillation. The oscillations are slowed down; in an actual tuned circuit the charge oscillates back and forth hundreds of thousands to billions of times per second.