Spule

Spule is a German noun with several related meanings. In electronics and electrical engineering, a Spule denotes a wound conductor that forms an inductor or a transformer winding. An inductor stores energy in a magnetic field when current passes through the winding, and two or more Spulen can transfer energy through mutual inductance in transformers. The inductance depends on the number of turns, the core material and geometry, and the arrangement (for example, an air-core, ferrite, or iron-core coil). A ferromagnetic core increases inductance by concentrating flux, while an air-core coil is typically used where low losses at high frequencies are important. In circuit design, inductors are used in filters, oscillators, impedance matching, and power supplies; their behavior is frequency-dependent, with parasitic capacitance and DC resistance affecting performance. Inductors are specified by inductance (henries) and current ratings, and high-frequency applications may employ Litz-wired windings to reduce AC losses.

Spule also means a spool or reel in everyday language. It refers to a cylindrical core around which wire, thread, cable, or magnetic tape is wound for storage and handling. The term spans contexts from textiles and manufacturing to data storage. The geometry and material of a spool influence winding density, unwinding smoothness, and wear on the stored material.

In both senses, the concept centers on a wound form that either stores magnetic energy as part of an electric circuit or serves as a practical means to wind and store materials.