An air-core coil is a type of coil that does not contain a magnetic core but instead relies on air or non-magnetic materials at its center. The structure of this coil is simple but effective: it consists of insulated wire wound into a spiral shape. When an electrical current passes through the coil, it generates a magnetic field around it. The strength of the magnetic field is directly proportional to the amount of current and the number of turns in the wire.

Air-core coils work based on the principle of electromagnetic induction, where a changing magnetic field interacts with the coil to produce electrical energy. This principle is used in a wide variety of devices, including relays, motors, transformers, wireless communication systems, and speakers, among others.

While the material used for winding the coil can vary—typically copper, aluminum, or other conductive metals—an air-core coil does not rely on any metal magnetic core. Instead, it functions with an empty or plastic core, which makes it ideal for applications where a strong, non-magnetic field is preferred.

Air-core coils are versatile and can be manufactured in different shapes, such as round, square, or oval, to meet specific application requirements. Whether used in high-frequency wireless devices or electromagnetic motors, the simplicity and effectiveness of air-core coils make them an essential component in modern electrical engineering.