LC Oscillations – Class 12 | Chapter – 7 | Physics Short Notes Series PDF for NEET & JEE
LC Oscillations: LC oscillations are a type of electrical oscillations that occur in a circuit containing an inductor (L) and a capacitor (C) connected in parallel or series. An LC circuit can store electrical energy in the magnetic field of the inductor and the electric field of the capacitor. When the circuit is initially charged or discharged, the stored energy is released, causing the current to flow back and forth between the inductor and the capacitor, creating a sustained oscillation.
In a series LC circuit, the voltage across the capacitor and the voltage across the inductor are out of phase by 180 degrees. Initially, when the capacitor is fully charged and the inductor has no current flowing through it, the capacitor starts to discharge through the inductor, creating a magnetic field around it. As the capacitor discharges, the voltage across the capacitor decreases, and the voltage across the inductor increases, causing the current to flow through the inductor. This current creates a magnetic field around the inductor, which stores the energy that was originally stored in the capacitor.
As the current continues to flow through the inductor, the capacitor begins to charge in the opposite direction. As the voltage across the capacitor increases, the voltage across the inductor decreases, causing the current to decrease. When the current reaches zero, the energy that was stored in the magnetic field of the inductor is transferred back to the electric field of the capacitor, which continues to charge. The process then repeats, with the energy flowing back and forth between the inductor and the capacitor, creating a sustained oscillation.
In a parallel LC circuit, the current through the inductor and the current through the capacitor are out of phase by 180 degrees, while the voltage across the inductor and the voltage across the capacitor are in phase. The oscillation in a parallel LC circuit is similar to that in a series LC circuit, with the energy flowing back and forth between the inductor and the capacitor.
Applications of LC Oscillations
LC oscillations have a wide range of applications in various fields of electrical and electronics engineering. Some of the key applications of LC oscillations are:
- Radio frequency (RF) circuits: LC oscillations are widely used in RF circuits for generating and receiving radio waves. LC oscillators are used to generate high-frequency signals in radio transmitters, while LC filters are used in radio receivers to filter out unwanted signals.
- Electronic clocks and timers: LC oscillators are used to generate stable clock signals in electronic circuits. The oscillations in an LC oscillator are highly predictable and can be tuned to generate precise frequencies, making them ideal for timekeeping applications.
- Filters and resonant circuits: LC circuits are used as filters and resonant circuits in a wide range of applications, including audio amplifiers, power supplies, and wireless communication systems. By varying the capacitance or inductance of the circuit, the resonant frequency of the circuit can be tuned to filter out unwanted signals or amplify desired signals.
- Antennas: LC circuits are used in antennas to tune the antenna to the frequency of the incoming signal. By adjusting the inductance or capacitance of the antenna circuit, the antenna can be tuned to receive signals at a specific frequency.
- Medical equipment: LC circuits are used in medical equipment such as magnetic resonance imaging (MRI) machines and electroencephalography (EEG) machines to generate and detect electromagnetic waves.
Audio equipment: LC oscillations are used in audio equipment such as guitar amplifiers and synthesizers to generate and filter sound signals. The oscillations can be tuned to generate specific frequencies and to filter out unwanted noise.
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