FISIKA Kelas 12 - Induksi Elektromagnetik: Induktansi Diri | GIA Academy

Summary

This educational YouTube video by Gia Akademi explores the concept of self-induction in electrical circuits. It explains how the gradual brightening and dimming of lights when switched on and off is due to the changing magnetic flux, inducing an electromotive force (EMF) that opposes the current change. The video delves into the principles of self-induction, including the formula for induced EMF, \( \varepsilon = -L \frac{\Delta I}{\Delta t} \), where \( L \) is the inductance, \( \Delta I \) is the change in current, and \( \Delta t \) is the change in time. It also covers the calculation of inductance in solenoids and toroids, the energy stored in inductors, and mutual inductance between two coils. The video concludes with practical examples and problems to solidify the understanding of self-induction.

Takeaways

• 🔌 The concept of self-induction is applied in everyday life, such as the gradual dimming of a light when switched off due to changes in magnetic flux.
• 💡 When turning on a light, the switch closes, and electricity flows through the circuit, creating a change in magnetic flux which causes the light to gradually brighten rather than instantly.
• 🌀 The gradual fading of a light when switched off is due to the change in magnetic flux as the electric current in the circuit is interrupted.
• ⚖️ The self-induced electromotive force (emf) is calculated using the formula ε = -L * (ΔI/Δt), where L is the self-inductance, and ΔI/Δt is the rate of change of current over time.
• 👨‍🔬 Joseph Henry, an American scientist, formulated the law stating that the magnitude of self-induced emf is proportional to the rate of change of current with respect to time.
• 🧲 The self-inductance of a coil can be determined by the formula L = n * ΔΦ/ΔI, where n is the number of turns, and ΔΦ is the change in magnetic flux.
• 📏 The self-inductance at the center of a solenoid can be calculated using the formula L = μ₀ * n² * a / l, with μ₀ being the permeability of free space.
• 🔗 The energy stored in a coil or inductor is given by the formula W = 1/2 * L * I², where W is the energy in joules, L is the inductance in henries, and I is the current in amperes.
• 🔄 Mutual or reciprocal inductance occurs between two coils when a changing current in one coil induces a changing magnetic flux in the other, calculated by M = N₁ * Φ₂ / I₂ = N₂ * Φ₁ / I₁.
• 📡 The inductance of a toroid can be determined using the formula L = μ₀ * N² * a / 2π, where a is the mean radius, N is the number of turns, and μ₀ is the permeability of free space.

Q & A

What is the concept of self-induction explained in the video?

Self-induction is a phenomenon where a changing electric current in a circuit induces an electromotive force (EMF) in the same circuit due to the change in magnetic flux. This concept is demonstrated through the example of a light bulb, which doesn't turn on or off instantly when the switch is flipped.

How is the EMF of self-induction calculated?

The EMF of self-induction is calculated using the formula ε = -L * (ΔI/Δt), where ε is the induced EMF, L is the self-inductance, and (ΔI/Δt) is the rate of change of current with respect to time.

Who is Joseph Henry and what is his contribution to the understanding of self-induction?

Joseph Henry was an American scientist who formulated the law of self-induction, stating that the magnitude of the induced EMF is proportional to the rate of change of the magnetic flux, which can be expressed as ε = -L * (dI/dt).

What is the unit of self-inductance and what is its symbol?

The unit of self-inductance is the Henry, symbolized as 'H'.

What is the relationship between the change in magnetic flux and the induced EMF according to Faraday's law?

According to Faraday's law, a change in magnetic flux through a coil induces an EMF in the coil, which is proportional to the rate of change of the magnetic flux, expressed as ε = -n * (ΔΦ/Δt), where n is the number of turns in the coil and ΔΦ is the change in magnetic flux.

How is the self-inductance of a solenoid calculated?

The self-inductance of a solenoid is calculated using the formula L = μ₀ * n² * A / l, where μ₀ is the permeability of free space, n is the number of turns per unit length, A is the cross-sectional area of the solenoid, and l is the length of the solenoid.

What is the energy stored in an inductor and how is it calculated?

The energy stored in an inductor is given by the formula W = 1/2 * L * I², where W is the energy in joules, L is the inductance in henries, and I is the current in amperes.

What is mutual induction and how does it differ from self-induction?

Mutual induction occurs when a changing current in one coil (primary) induces a current in a nearby coil (secondary) due to the changing magnetic field. It differs from self-induction, which occurs within the same coil. Mutual induction is calculated using the formula M = N₁ * Φ₂ / I₂ = N₂ * Φ₁ / I₁, where M is the mutual inductance, N₁ and N₂ are the number of turns in the primary and secondary coils, and Φ₁ and Φ₂ are the magnetic fluxes in the primary and secondary coils, respectively.

How is the self-inductance of a toroid calculated?

The self-inductance of a toroid is calculated using the formula L = μ₀ * n² * A / (2π), where μ₀ is the permeability of free space, n is the number of turns, A is the cross-sectional area, and the division by 2π accounts for the toroid's geometry.

What is the significance of the problem-solving examples provided in the video?

The problem-solving examples in the video demonstrate the practical application of the concepts of self-induction, mutual induction, and energy storage in inductors. They help in understanding how to calculate the induced EMF, self-inductance, and stored energy in different types of inductors.