Induktori

Induktori are passive electrical components that store energy in a magnetic field when current flows through a coil of conductor. They oppose changes in current, in accordance with Lenz's law, and are widely used in analog and power electronics.

Construction and basic principle: an inductori consists of a wire wound into one or more turns around a core made of air or soft magnetic material such as iron or ferrite. The core concentrates the magnetic flux and increases the inductance. The inductance L depends on the number of turns, the cross-sectional area of the core, the length of the magnetic path, and the core material’s permeability. A simple expression for a coil with a uniform core is L ≈ μ N^2 A / l, where μ is the permeability, N the number of turns, A the cross-sectional area, and l the magnetic path length.

Electrical characteristics: in AC circuits, the impedance of an inductori is Z = R + jωL, where R is the winding resistance and ω is the angular frequency. The inductive reactance is X_L = ωL, and the energy stored in the magnetic field is E = 1/2 L I^2. Real inductors exhibit parasitic elements such as winding resistance, parasitic capacitance, core losses, and, at high flux, core saturation.

Types and formats: inductori come in a variety of forms, including air-core, iron-core, and ferrite-core types; toroidal, axial-lead, radial-lead, and surface-mount configurations; designed for different frequency ranges and power levels. They are commonly used in filters, tuned circuits, power supplies, chokes, and transformer assemblies where two inductors are magnetically coupled.

Applications and limitations: inductors are essential in LC networks for filtering and resonance, in energy storage for switching power supplies, and in impedance matching. Limitations include size, saturation, tolerance, and a tendency for performance to vary with temperature and frequency. The concept of inductors dates to early 19th-century experiments on induction.