By Laurie Brenner, Updated Aug 30, 2022
An everyday handheld speaker or any device with a speaker contains a tiny electromagnet—also known as a voice coil—inside its driver. This electromagnet converts electrical signals into mechanical vibrations that move the cone or diaphragm, producing sound. Whenever a device requires a changing current to perform a task, an electromagnet is often at work.
Electromagnets consist of a coil of copper wire wound around a magnetic core, typically iron. When electric current flows through the coil, it generates a magnetic field that is concentrated by the core. If the current stops, the magnetic field collapses, and the electromagnet loses its magnetism. By adjusting the current, the magnetic field can be strengthened or weakened, allowing precise control—something permanent magnets cannot provide.
In a speaker, the voice coil moves in response to the electrical audio signal, causing the cone to vibrate. In a hard‑disk drive, a miniature electromagnet inside the read/write head magnetizes tiny sectors on the disk, writing binary data (0s and 1s). The same head reads the magnetized sectors to retrieve information.
Electromagnets are critical in maglev trains, where they generate the lift and propulsion needed for frictionless travel. In medical imaging, superconducting electromagnets produce the strong, stable magnetic field required for magnetic‑resonance imaging (MRI). Power transformers on the grid use electromagnets to step down high‑voltage transmission to household‑level voltages.
Devices such as washing‑machine solenoid valves, garbage disposals, microwave ovens, and induction cooktops contain electromagnets that control water flow, motor operation, or heating elements. Even older tape recorders and VCRs used electromagnets to record and play audio and video.
From the music you enjoy to the data stored on your hard drive, electromagnets are an essential component of modern technology. Their ability to switch on and off, and to adjust magnetic strength on demand, makes them indispensable for a wide range of applications.
