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Just a pair of metal plates separated by a small distance is called "capacitor". It can store electric field(charges) and release it.
A coil of wire can create magnetic field when electric current is passed through it. Magnetic field depends on the strength of the current. A coil of conductor is called an "inductor".
Let us connect a battery for some time to the capacitor till it fully charges up. Next we will connect the capacitor and the inductor in parallel. Now the actions starts.
- The capacitors slowly discharges, current flows in the circuit and magnetic field builds up in the coil.
- When the capacitor is fully discharged, the magnetic field of the coil starts to collapse and the current flows(Faraday's law) in the same direction. At the same time the capacitor is charged up in the opposite direction.
- When the coil fully loses magnetic field, the capacitor starts to send the current in the opposite direction. The cycle goes on.
Thus we get alternating current(sinusoidal current) from the circuit. The pendulum oscillates by alternating between kinetic and potential energy. Here the current oscillates by alternating between electric and magnetic energy.
Two very simple components create electric oscillations. It is a thing of wonder.
This circuit is also called tank circuit(because it stores up energy) and it is a basic and an important circuit in electronics.
Note: The electric oscillations will be slowly damped due to natural resistance in the circuit.
