Inductance determinants — Which set of properties primarily controls the inductance value of a coil (assume a uniform core and tightly wound turns)?

Introduction:
Designing inductors requires understanding which geometric and material factors set the inductance. This knowledge guides core selection and winding specifications for filters, chokes, and transformers.

Given Data / Assumptions:

• Coil wound uniformly on a magnetic path with effective length l and cross-sectional area A.
• Permeability μ depends on the core material (air, iron, ferrite, etc.).
• Skin and proximity effects ignored for the inductance value itself.

Concept / Approach:

A simplified form shows L proportional to μ * N^2 * A / l. Thus inductance increases with higher permeability, more turns, and larger core area, and decreases with longer magnetic path length. Wire type (gauge) affects resistance and current rating, not the magnetostatic inductance directly.

Step-by-Step Solution:

Verification / Alternative check:

Inductor design calculators and core datasheets apply exactly these variables, confirming the proportionality and practical design steps for target inductance values.

Why Other Options Are Wrong:

• Options with “type of wire” or “length of wire” emphasize resistance/temperature rise, not inductance.
• Irrelevant attributes (color, solder type) do not affect L.

Common Pitfalls:

• Confusing DC resistance effects with inductance; both matter but are distinct.
• Ignoring fringing and air-gap effects in gapped cores that reduce μ and L.

Final Answer:

Type of core material, number of turns, cross-sectional area of core, and length of core