Editing LC circuit (section)

==Operation==
[[Image:Tuned circuit animation 3 300ms.gif|thumb|Animated diagram showing the operation of a [[tuned circuit]] (LC circuit). The capacitor C stores energy in its [[electric field]] {{mvar|E}} and the inductor L stores energy in its [[magnetic field]] {{mvar|B}} ''(<span style="color:green;">green</span>)''. The animation shows the circuit at progressive points in the oscillation. The oscillations are slowed down; in an actual tuned circuit the charge may oscillate back and forth thousands to billions of times per second.]]

An LC circuit, oscillating at its natural [[resonant frequency]], can store [[electrical energy]].  See the animation.  A capacitor stores energy in the [[electric field]] ({{mvar|E}}) between its plates, depending on the [[voltage]] across it, and an inductor stores energy in its [[magnetic field]] ({{mvar|B}}), depending on the [[Electric current|current]] through it.

If an inductor is connected across a charged capacitor, the voltage across the capacitor will drive a current through the inductor, building up a magnetic field around it. The voltage across the capacitor falls to zero as the charge is used up by the current flow. At this point, the energy stored in the coil's magnetic field induces a voltage across the coil, because inductors oppose changes in current. This induced voltage causes a current to begin to recharge the capacitor with a voltage of opposite polarity to its original charge. Due to [[Faraday's law of induction|Faraday's law]], the [[electromotive force|EMF]] which drives the current is caused by a decrease in the magnetic field, thus the energy required to charge the capacitor is extracted from the magnetic field. When the magnetic field is completely dissipated the current will stop and the charge will again be stored in the capacitor, with the opposite polarity as before. Then the cycle will begin again, with the current flowing in the opposite direction through the inductor.

The charge flows back and forth between the plates of the capacitor, through the inductor. The energy oscillates back and forth between the capacitor and the inductor until (if not replenished from an external circuit) internal [[Electrical resistance|resistance]] makes the oscillations die out.  The tuned circuit's action, known mathematically as a [[harmonic oscillator]], is similar to a [[pendulum]] swinging back and forth, or water sloshing back and forth in a tank; for this reason the circuit is also called a ''tank circuit''.<ref name="Rao">{{cite book
 | last1 = Rao
 | first1 = B. Visvesvara| title = Electronic Circuit Analysis
 | publisher = Pearson Education India
 | date = 2012
 | location = India
 | pages = 13.6
 | url = https://books.google.com/books?id=wyQ8BAAAQBAJ&q=%22tank+circuit%22+water&pg=SA13-PA6
 | isbn = 978-9332511743
 |display-authors=etal}}</ref> The [[natural frequency]] (that is, the frequency at which it will oscillate when isolated from any other system, as described above) is determined by the capacitance and inductance values.  In most applications the tuned circuit is part of a larger circuit which applies [[alternating current]] to it, driving continuous oscillations. If the frequency of the applied current is the circuit's natural resonant frequency ([[natural frequency]] <math>f_0\,</math> below), [[resonance]] will occur, and a small driving current can excite large amplitude oscillating voltages and currents.  In typical tuned circuits in electronic equipment the oscillations are very fast, from thousands to billions of times per second.{{Citation needed|date=April 2022}}