How Inductors Work: Energy Storage, Back EMF, and Circuits | Engineering Mindset

Overview

This video from Engineering Mindset explains inductors, showing how they store energy in a magnetic field and release it quickly. Using a water pipe analogy, the host compares the inductor to a heavy water wheel and explains back EMF, why inductors resist changes in current, and what happens when a circuit includes an inductor in parallel with a lamp. The summary also notes practical aspects like how inductors look on boards, the symbols used in diagrams, and common applications such as boost converters, filters, transformers, motors and relays. It also covers measuring inductance and why a standard multimeter isn’t enough for accurate results.

Introduction to Inductors

Inductors are fundamental circuit components that store energy in a magnetic field created by current flowing through a coil. The video begins by defining an inductor as a device that can hold energy and release it quickly, which is essential for many electronic applications. It emphasizes the importance of understanding how inductors differ from capacitors, which store energy electrostatically rather than magnetically.

What Is an Inductor

The presenter explains inductors as coils that generate a magnetic field when current passes through them. The magnetic field stores energy, and when current changes, the field collapses or builds, converting energy back into electrical energy. This dynamic is central to how inductors influence circuit behavior, especially during transitions on and off power supplies.

The Water Pipe Analogy

A key teaching tool in the video is a water flow analogy. A battery acts as the pump, the pipe network as conductors, and a reducer in one branch represents resistance. The water wheel in another branch represents the inductor. Because the wheel is heavy, it takes time to reach speed, resisting changes in current and creating back EMF as current rises. When power is cut, the wheel’s inertia helps push current, showing how energy is stored and released by the magnetic field of the inductor.

Back EMF and Current Behavior

The video explains back EMF as the opposing force generated when current through an inductor changes. When the circuit turns on, the inductor resists the initial surge, causing a gradual current rise. As the magnetic field grows, the current stabilizes and the inductor effectively becomes a normal wire. When power is removed, the stored energy drives current, helping to maintain current flow until the field collapses.

Inductors in Circuits

The demonstration of an inductor in parallel with a lamp shows how current initially favors the lamp, then gradually shifts to the inductor as it reduces resistance. When the power returns, the lamp may light again due to the transient behavior before the energy is dissipated by the circuit resistance. The host highlights practical intuition for when to expect inductors to dominate circuit behavior during switching events.

Visualizing Magnetic Fields

The magnetic field is described as something that can be visualized with compasses around a wire, showing how the field direction follows current. When the wire is wound into a coil, the fields reinforce, creating a stronger storage mechanism. The concept of magnetic flux lines is illustrated with iron filings, helping viewers understand the invisible energy storage in inductors.

Inductor Form Factors and Symbols

The video notes that inductors on circuit boards typically appear as wrapped copper wires around a cylinder or ring, sometimes enclosed to shield the magnetic field from interfering with nearby components. In engineering drawings, inductors are represented with standard symbols, and the broader principle is that any coiled conductor can function as an inductor.

Applications of Inductors

Inductors find use in boost converters to increase DC voltage, as chokes to filter or pass DC, in filtering to separate frequencies, and in power components such as transformers, motors and relays. These uses illustrate why inductors are ubiquitous in electronics, from power supplies to signal processing and motor control.

Measuring Inductance

Inductance is measured in henries, with larger values indicating greater energy storage and longer field build time. The video points out that a standard multimeter cannot accurately measure inductance—some models include a test function, but accuracy depends on the instrument. For precise measurements, an LCR meter is used to determine inductance values by injecting a small AC signal and analyzing the response of the circuit.

Putting It All Together

By combining theoretical explanations with visuals and practical notes, the video provides a coherent foundation for understanding inductors. It ties together the physics of magnetic energy storage, the dynamic response to current changes, schematic representations, and real-world applications. The viewer is guided toward deeper learning through related videos on the channel and the broader engineering concepts behind inductors.

Further Learning

As with other Engineering Mindset lessons, viewers are encouraged to explore linked videos for more detail on related topics such as capacitors, circuit analysis, and measurement techniques.