# Operation Of LC circuit

## I generally can't understand the operation of an LC circuit that is I cannot visualize it. I have a few doubts regarding that, please explain me?

Operation:

Animated diagram showing the operation of a tuned circuit (LC circuit).The oscillations are slowed down; in an actual tuned circuit the charge oscillates back and forth tens of thousands to billions of times per second.

If a charged capacitor is connected across an inductor, current will start to flow through the inductor, building up a magnetic field around it and reducing the charge, and therefore 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 unchanged in accordance with Faraday's law of induction, which requires that for the current to change in an inductor, a voltage must be applied to it (this is analogous to Newton's First Law for velocity, mass and force). No energy is required for this provided the current remains constant. However, as the current continues to flow, the capacitor will re-acquire charge of the opposite sign, and its terminal voltage will rise again with reversed polarity. This applies a voltage to the inductor which is now in opposition to its current, so the current now falls. Again this in accordance with Faraday's Law. The falling inductor current and rising capacitor voltage indicate a transfer of energy from the inductor to the capacitor. This is analogous to a moving mass colliding with a spring, and compressing it. When the magnetic field has completely dissipated the current will momentarily stop, and the charge will again be stored in the capacitor, with a polarity opposite to its original one. This will complete half a cycle of the oscillation. The process will then begin again in reverse, with the current flowing in the opposite direction through the inductor. For more details visit http://en.wikipedia.org/wiki/LC_circuit where I found this stuff.

Doubts:-

1. At the beginning 5v appears across the inductor, after that instant current flowing must increase in the inductor, since the current flows through the inductor to the opposite plate of the capacitor the charges are neutralised. Eventually the voltage across the capacitor decreases, This must lead to decrease in voltage across the inductor also, which then causes the current to increase slowly inside an inductor and thus when the voltage is zero across the capacitor , current must be almost zero in the inductor.....But it is assumed that 5v appears across the inductor constantly no matter what is the voltage across the capacitor. Why is it assumed so, due to this assumption we have charging and discharging across the capacitor??

2. Let that assumption be true (Consider),Then after the capacitor has reached zero volts, it is said that the current still flows, But where is the source of charge for it. Without charge how can current flow, i.e there is no source no electrons or positive ions for the current to flow, Doesn't this disobey the law of conservation of energy.

3. Can anyone please explain to me this circuit conceptually?

• Did you completely skip over the description of the magnetic field in the theory of operation? Mar 8, 2015 at 5:46
• I found this @wikipedia Mar 8, 2015 at 5:50
• en.wikipedia.org/wiki/LC_circuit Mar 8, 2015 at 5:51
• That's not what I asked. Mar 8, 2015 at 5:51
• No,I didn't skip them. Mar 8, 2015 at 5:53