An inductor is a key electronic component that temporarily holds energy in a magnetic field when current flows through its coil. It’s usually made up of two terminals and a insulated wire coil. Often referred to as coils, chokes, or reactors in older texts, inductors play a crucial role in managing current fluctuations in circuits.
When electricity travels through a conductor like copper wire, it creates a magnetic field. Shaping this wire into a coil amplifies that magnetic field’s strength. Wrapping the coil around a core made of iron makes it even stronger—this principle is behind how electromagnets work. The electricity determines the magnetic field’s strength, and any shifts in the current alter the field.
Inductors are essential for smoothing out those current fluctuations. When current enters the inductor’s coil, the magnetic field grows until it stabilizes. During that initial phase, the coil resists the current flow. Once the field stabilizes, normal current passes through. As long as the current continues, energy gets stored in that magnetic field. When the current stops, the magnetic field collapses, converting the stored magnetic energy back into electrical energy, feeding it back into the circuit until everything settles.
If the current flow is steady, it behaves like any regular wire. But with sudden changes, the inductor pushes back, making the current lag behind the voltage due to its magnetic field. As the current changes, so does the magnetic field—growing with increases and shrinking with decreases. These changes in the magnetic field induce an electromagnetic field that opposes the current change: trying to boost it when it dips and reduce it when it spikes.
The inductor’s resistance to these changes is called inductance, measured in henries (H). Due to the henry being a sizable unit, we often use millihenries (mH) and microhenries (µH). Various factors can influence an inductor’s inductance, such as the number of coils, wire length, core material, and even the coil’s size and shape.
Core materials significantly affect inductance. Air cores provide the least inductance, while materials like wood or glass have similar properties to air. Ferromagnetic materials like iron can boost inductance considerably—sometimes by thousands of times. The core’s shape impacts efficiency, with toroidal or donut-shaped cores being more effective than cylindrical ones.
Creating inductors on integrated circuit (IC) chips is challenging but possible, albeit with lower inductance. Sometimes, engineers simulate inductance using other components like transistors and capacitors on ICs.
Inductors and electrical transformers share similarities, utilizing wound coils and ferrous cores to create electromagnetic fields for energy storage and conversion.
Now, what sets inductors apart from capacitors? Both are fundamental components in circuits, but they store energy differently. Inductors hold energy as magnetic flux, while capacitors store it as an electric field. With an inductor, current initially resists flow, and when it stabilizes, it accepts flow. In contrast, a capacitor allows initial current but blocks it when fully charged.
Inductors block high-frequency signals, permitting low frequencies and direct current. Capacitors do the opposite: they resist direct current and low frequencies while allowing higher frequencies to pass.
So, where do we use inductors? They often act as filters, blocking unwanted high-frequency noise. For example, they can smooth out higher harmonics in power supplies, ensuring a clean 50/60 Hz frequency. Pairing inductors with capacitors lets only specific frequencies through, useful in radio tuning and applications like Wi-Fi and 5G to minimize interference.
Inductors are also found in switching power supplies, where they store energy as circuits toggle on and off, enabling control over output voltage efficiently.