Inductors Explained: How They Work, Where They're Used, and Why They Matter

Overview

In this Engineering Mindset video, Paul explains inductors, what they are, how they store energy in a magnetic field, and why they matter in circuits. The water flow analogy helps visualize how current is initially resisted, how a heavy water wheel represents the inductor, and how energy can be released back into the circuit when the supply is removed. The video then shows inductors in parallel with a lamp, highlighting back EMF and the shift of current as the inductor's resistance changes. It also covers what inductors look like, how they are drawn in schematics, common uses such as boost converters and filters, and how to measure inductance with an RLC meter.

What is an inductor

An inductor is a passive circuit element that stores energy in its magnetic field when current flows through a coil of wire. The energy storage allows it to release energy quickly when the circuit conditions change, a feature that makes inductors essential in many applications from power supplies to signal processing.

Energy storage and back EMF

As current builds, a magnetic field stores energy. If the current tries to change, the inductor resists this change by generating a back electromotive force, or back EMF, which opposes the original change in current. When the source is removed, the magnetic field collapses and helps push current to keep the circuit momentarily alive, before the energy is dissipated as heat.

The water flow analogy

Paul uses a pump as a battery, pipes as conductors, and a wheel in one branch to represent the inductor. The wheel’s inertia makes it slow to start, increasing the resistance on that path, so current initially flows through the other branch. As the wheel speeds up, it becomes the preferred path, and when the pump stops, the wheel keeps the water moving briefly before the system settles.

Inductors in circuits

In a circuit where an inductor is in parallel with a lamp, the lamp may initially light as current divides, but over time the inductor’s decreasing impedance pulls current away from the lamp, turning it off. When the power is disconnected, the inductor continues to drive current until its stored energy is exhausted.

Visualization and measurement

Magnetic fields form around current-carrying wires and coils. Compasses align with the magnetic field, and iron filings reveal flux lines around magnets and coils. Inductance is measured in henries (H) using an RLC meter because a standard multimeter cannot give precise results for inductors. The meter applies a test signal and calculates the inductance value from the coil behavior.

Appearance, symbols, and uses

Inductors on boards are typically copper wire wound around a cylinder or ring, sometimes enclosed to shield the magnetic field. In schematics they are shown with the standard inductive symbol. Everything that uses a coil can be an inductor including motors, transformers and relays. Common uses include boost converters to increase the output voltage, chokes to filter or isolate AC from DC, and various filtering and energy storage tasks in power electronics and signal paths.

Measuring inductance and practical notes

Inductance is measured in henries, and accuracy depends on using the right instrument such as an RLC meter. A multimeter may offer a rough reading on some models, but dedicated inductance meters provide better accuracy. Remember that inductors store energy in a magnetic field only while current flows; the field collapses when current ceases, returning energy to the circuit as back EMF or dissipating it as heat.

Key takeaways

Inductors resist changes in current, store energy in a magnetic field, and release that energy when needed. They are essential components in power conversion, filtering, and energy management across a wide range of electrical systems, and their behavior can be studied visually through magnetic field demonstrations and measured with proper instruments.