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How do electromagnets work in telephone receivers and loudspeakers?

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In both telephone receivers and loudspeakers, electromagnetic principles are used to convert fluctuating electrical signals into sound waves through the interaction of magnetic fields and moving parts.12

Telephone Receivers

A telephone receiver functions as an electromagnet, typically consisting of a U-shaped yoke with coils of wire wound around its legs. When an audio-frequency electrical signal passes through these coils, it creates a varying magnetic field. This field changes the attraction of the magnet for a nearby soft-iron diaphragm. As the diaphragm is deflected in proportion to the current, it vibrates back and forth, pushing the air to generate sound waves that reproduce speech.31

Loudspeakers

Loudspeakers operate on a similar principle but are designed to displace a larger volume of air. They feature a "voice coil" attached to a flexible cone (diaphragm) that is suspended within the gap of a powerful permanent magnet. When a time-varying electrical current flows through the voice coil, it creates a magnetic force that causes the coil and the attached cone to move. This oscillation converts the electrical energy into pressure waves, which we perceive as sound.32