How does magnetic recording use an electromagnet to store sound or computer information?

Magnetic recording uses an electromagnet to convert electrical signals into a permanent magnetic pattern on a storage medium, such as tape or disk.12

The Recording Process

The recording head typically consists of a U-shaped magnet yoke with coils wound around it. As an electrical signal—representing sound or computer data—passes through these coils, it creates a time-varying magnetic field within the gap of the magnet. As the magnetic medium (coated with particles like iron oxide) moves past this gap at a constant speed, the varying magnetic field induces a corresponding magnetization in the material.132

• Sound: The amplitude of the signal determines the extent of the magnetization, while the frequency determines the distance along the medium over which the field is reversed.3
• Computer Information: Data is stored as a chain of electrical pulses. Because this information is binary, the system simply needs to ensure the medium does not spontaneously demagnetize, allowing for high-density storage.12

Playback

To retrieve the information, the process is reversed: the magnetized medium passes by a coil, where the changing magnetic flux induces an electrical current that mirrors the original signal.12