Which factor affects the inductance of a coil?

The inductance of a coil is significantly influenced by the core cross-section area. When considering inductance, one must recognize that it is a measure of a coil’s ability to store energy in a magnetic field while current flows through it. A larger core cross-section area allows for a greater volume of magnetic field lines to be concentrated, which increases the inductance.

This increase occurs because with a larger area, the coil can link more magnetic flux, which enhances its ability to oppose changes in current according to Faraday's law of electromagnetic induction. Consequently, as the core area expands, the inductance also expands proportionately.

Understanding this principle is crucial in designing inductors and transformers, where optimization of inductance is necessary for efficient operation in various electronic circuits. By contrast, the other factors listed do not have the same direct impact on inductance changes, underscoring the importance of core geometry in inductor design.