LC circuit: Difference between revisions

Revision as of 13:51, 20 September 2018

Revision as of 21:18, 5 December 2018

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[[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 at right. 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, current will start to flow through the inductor, building up a magnetic field around it and reducing the voltage on the capacitor. Eventually all the charge on the capacitor will be gone and the voltage across it will reach zero. However, the current will continue, because inductors oppose changes in current. The current will begin to charge 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.