Electrical SHM – LC Oscillator - 2.2 | Simple harmonic motion, damped and forced simple harmonic oscillator | Physics-II(Optics & Waves)
K12 Students

Academics

AI-Powered learning for Grades 8–12, aligned with major Indian and international curricula.

Academics
Professionals

Professional Courses

Industry-relevant training in Business, Technology, and Design to help professionals and graduates upskill for real-world careers.

Professional Courses
Games

Interactive Games

Fun, engaging games to boost memory, math fluency, typing speed, and English skills—perfect for learners of all ages.

games

Interactive Audio Lesson

Listen to a student-teacher conversation explaining the topic in a relatable way.

Introduction to LC Oscillator

Unlock Audio Lesson

Signup and Enroll to the course for listening the Audio Lesson

0:00
Teacher
Teacher

Today we will explore Electrical Simple Harmonic Motion, specifically focusing on the LC oscillator. Can anyone tell me what components are involved in an LC circuit?

Student 1
Student 1

Isn't it a capacitor and an inductor?

Teacher
Teacher

Exactly! An LC circuit consists of an inductor, L, and a capacitor, C. When connected, they produce oscillatory behaviour. The governing equation for this system is expressed as L d²q/dt² + (1/C)q = 0. The charge q represents the energy stored in the capacitor.

Student 3
Student 3

What does that equation mean in terms of oscillations?

Teacher
Teacher

Good question! This equation indicates that the charge on the capacitor oscillates over time, just like a mass-spring system. Similar to mechanical SHM where F = -kx, here the charge is governed by its relation to the circuit components.

Student 4
Student 4

What about the angular frequency? How do we relate that?

Teacher
Teacher

The angular frequency for an LC oscillator is determined by the formula \(\omega = \sqrt{\frac{1}{LC}}\). This tells us how fast the oscillations occur based on the inductance and capacitance values.

Teacher
Teacher

To recap, the LC circuit’s behaviour is analogous to mechanical oscillators, where charge corresponds to displacement, and it's essential for understanding electrical systems.

Current Behaviour in LC Oscillator

Unlock Audio Lesson

Signup and Enroll to the course for listening the Audio Lesson

0:00
Teacher
Teacher

Now, let’s discuss how current behaves in an LC circuit. Can anyone tell me the equation for current?

Student 2
Student 2

I think it relates to the charge, right?

Teacher
Teacher

Exactly! The current can be expressed as \(i(t) = \frac{dq}{dt} = -Q\omega \sin(\omega t + \phi)\). Here, Q is the peak charge, and \(\phi\) is the phase constant.

Student 1
Student 1

So, how does the current relate to the oscillations?

Teacher
Teacher

The negative sign indicates that the current will oscillate in response to the changing charge in the capacitor. This oscillation reflects the energy transfer between the inductor and capacitor.

Student 4
Student 4

Can we compare this to mechanical systems?

Teacher
Teacher

Yes! In mechanical systems, velocity corresponds to the rate of displacement change – just like how our current is elaborately dependent on the changing charge in electrical systems. It’s a beautiful analogy!

Teacher
Teacher

To summarize, the current in an LC oscillator presents a sine wave behaviour linked directly to the charge on our capacitor and angular frequency.

Analogy Between Mechanical and Electrical Oscillations

Unlock Audio Lesson

Signup and Enroll to the course for listening the Audio Lesson

0:00
Teacher
Teacher

Let’s wrap our head around the analogies between mechanical and electrical SHM. We’ve already touched on this. What components correspond in electrical circuits and mechanical systems?

Student 3
Student 3

The inductor corresponds to mass, and the capacitor corresponds to a spring, right?

Teacher
Teacher

Exactly! And displacement in mechanical systems corresponds to charge in an electrical circuit. This analogy helps us easily understand complex circuit behaviours by relating them to familiar physical concepts.

Student 2
Student 2

Why is it important to understand this analogy?

Teacher
Teacher

Understanding this analogy is critical in modern technology like signal processing and communications. Electrical oscillators play a key role in how we transfer information.

Student 4
Student 4

Can you summarize the key points from this section?

Teacher
Teacher

Certainly! We learned that LC circuits demonstrate electrical SHM with governing equations, analogies to mechanical systems, and the importance of these concepts in modern applications.

Introduction & Overview

Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.

Quick Overview

This section introduces the concept of Electrical Simple Harmonic Motion through the study of LC oscillators and their equations.

Standard

The section covers the fundamental principles of electrical SHM using LC circuits. It explains the governing equations, angular frequency, and current behaviour while drawing analogies to mechanical SHM. The significance of understanding electrical oscillators in modern technology is also highlighted.

Detailed

Electrical SHM – LC Oscillator

This section delves into the phenomenon of Electrical Simple Harmonic Motion (SHM) by focusing on an LC oscillator, which includes an inductor (L) and a capacitor (C) arranged in series. The governing equation for this circuit is expressed as:

$$ L \frac{d^2q}{dt^2} + \frac{1}{C} q = 0 $$

where:
- q is the charge on the capacitor.

From this relationship, we derive that the angular frequency of electrical oscillation is:

$$ \omega = \sqrt{ \frac{1}{LC} } $$

This implies that, similar to mechanical oscillators, electrical oscillators have a natural frequency dependent on their physical components. The current through the circuit can also be expressed as:

$$ i(t) = \frac{dq}{dt} = -Q \omega \sin(\omega t + \phi) $$

where Q is the peak charge and ϕ is the phase constant. A notable aspect is the analogy to mechanical SHM, where mass corresponds to inductance (L), the charge to displacement (x), and the voltage across the capacitor to the restoring force, thereby reinforcing the concepts of energy conservation across both systems.

Further, studying electrical oscillators is crucial because they serve as the backbone for various technologies in communication systems, signal processing, and electronic circuits. The similarity in behaviour oscillations of mechanical and electrical systems fosters a deeper understanding of dynamics in both mediums.

Audio Book

Dive deep into the subject with an immersive audiobook experience.

LC Circuit Overview

Unlock Audio Book

Signup and Enroll to the course for listening the Audio Book

An LC circuit consists of an inductor L and capacitor C connected in series.

Detailed Explanation

An LC circuit is a type of electrical circuit that includes two key components: an inductor and a capacitor. The inductor (L) stores energy in a magnetic field when electrical current flows through it, while the capacitor (C) stores energy in an electric field. When these components are connected in series, they can oscillate, leading to a phenomenon similar to mechanical oscillations, where energy continuously shifts between the inductor and capacitor.

Examples & Analogies

Think of the LC circuit like a swing. Just as a swing moves back and forth between two positions, the energy in the LC circuit continuously moves between the inductor and the capacitor. When the capacitor is fully charged, it releases energy to the inductor, which then generates a current. This action is much like the swing reaching a maximum height, where it has potential energy before moving back down.

Governing Equation of LC Oscillator

Unlock Audio Book

Signup and Enroll to the course for listening the Audio Book

Governing equation:
Ld²q/dt² + 1/C q = 0 where q is charge on the capacitor.

Detailed Explanation

The governing equation for the LC oscillator describes how the charge (q) on the capacitor evolves over time. It implies that the second derivative of charge with respect to time (d²q/dt²) is proportional to the negative charge itself. This negative relationship indicates that as the charge increases, the restoring force pushing it back decreases, which leads to oscillation. Essentially, this equation helps us predict how the charge will change as time progresses, exhibiting oscillatory behavior.

Examples & Analogies

You can think of a roller coaster at its highest point. As it starts to roll down, gravity pulls it back down, converting potential energy into kinetic energy. Similarly, the charge on the capacitor experiences a push and pull as the circuit oscillates. The equation captures this relationship, just like physics describes how a roller coaster moves along its tracks.

Angular Frequency in LC Oscillator

Unlock Audio Book

Signup and Enroll to the course for listening the Audio Book

Angular frequency:
ω = 1/√(LC)

Detailed Explanation

The angular frequency (ω) of the LC oscillator determines how quickly the circuit oscillates. This formula shows that the angular frequency is inversely proportional to the square root of the product of the inductance (L) and capacitance (C). Hence, if either the inductance or capacitance is large, the frequency at which the circuit oscillates is lower, and vice versa. This relation is crucial for designing circuits that operate at specific frequencies.

Examples & Analogies

Imagine a child's playground swing: the heavier the swing (analogous to larger inductance) or the wider the swing's arcs (analogous to larger capacitance), the slower the swing will return to its starting position. This is similar to how the LC circuit's frequency decreases with increased L or C.

Current in the LC Circuit

Unlock Audio Book

Signup and Enroll to the course for listening the Audio Book

Current:
i(t) = dq/dt = -Qωsin(ωt + ϕ)

Detailed Explanation

The current in the LC circuit is derived from the change in charge with respect to time. It shows that the current is proportional to the negative of the charge multiplied by the angular frequency and the sine of the angular position at a given time (ωt + ϕ). This indicates that the current and charge are out of phase, reflecting the energy conversion dynamics between the capacitor and inductor during oscillation.

Examples & Analogies

You might imagine a metronome: as it swings from one side to the other, it ticks. The position of the metronome corresponds to the charge on the capacitor while the ticking represents the current. Just like the metronome reaches its peak position (high charge) and then falls back again, the current flows in alternating directions as the charge oscillates.

Definitions & Key Concepts

Learn essential terms and foundational ideas that form the basis of the topic.

Key Concepts

  • Governing Equation: The equation governing an LC circuit demonstrates establishing oscillatory motion.

  • Charge and Current: Charge and current are central to understanding LC oscillators and their dynamics.

  • Analogies: Mechanical and electrical systems share significant analogies that aid in comprehension of oscillatory behaviour.

Examples & Real-Life Applications

See how the concepts apply in real-world scenarios to understand their practical implications.

Examples

  • A typical LC circuit comprises a 10 mH inductor and a 100 µF capacitor, resulting in an angular frequency of approximately 5.03 Hz.

  • In a radio transmitter, LC circuits are utilized to generate radio waves, oscillating between energy storage in the inductor and capacitor.

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🎵 Rhymes Time

  • LC circuit, charge in tow, oscillating high and low!

📖 Fascinating Stories

  • Imagine L and C as friends on a swing, pushing and pulling in a harmonious rhythm, representing the charge and current in an LC circuit.

🧠 Other Memory Gems

  • Remember Light Cycles for LC circuits - with inductor (L) and capacitor (C) producing oscillations!

🎯 Super Acronyms

LC = Lightning Charge, associated with immediate oscillations due to rapid charging.

Flash Cards

Review key concepts with flashcards.

Glossary of Terms

Review the Definitions for terms.

  • Term: Capacitor

    Definition:

    A device that stores electrical energy in an electric field.

  • Term: Inductor

    Definition:

    A passive electrical component that stores energy in a magnetic field when an electric current flows through it.

  • Term: Oscillation

    Definition:

    A repeated variation in some measure about a central value.

  • Term: Angular Frequency

    Definition:

    A measure of rotation rate; it denotes how many cycles occur in a unit of time.

  • Term: Phase Constant

    Definition:

    A constant that determines the initial angle of the oscillating quantity.