induktorer

Induktorer, or inductors, are passive electrical components that store energy in a magnetic field created by current flowing through a coil of wire. The key quantity is inductance, measured in henries (H). The energy stored is 1/2 L I^2, and an inductor tends to oppose changes in current. The inductance depends on the number of turns, the cross-sectional area of the coil, its length, and the magnetic properties of the core. For a simple air‑core solenoid, L is approximately μ0 N^2 A / l.

Induktorer come in several forms. Air‑core inductors use air or nonmagnetic material as a core, while ferrite or iron‑core inductors employ magnetic materials to increase inductance and current handling. Toroidal inductors confine the magnetic field to the core, reducing stray fields. Power inductors are designed for higher current ratings and may use ferrite cores and protective packaging. There are also choke inductors for suppression of unwanted signals, as well as RF and variable inductors with adjustable cores.

Electrically, the impedance of an inductor is X_L = 2π f L, so inductors behave differently across frequencies. At higher frequencies, parasitic capacitance and core losses become important, leading to a self‑resonant frequency where the inductor ceases to behave ideally. Key design considerations include saturation current, quality factor (Q), equivalent series resistance (ESR), temperature dependence, and physical size.

Applications include filtering in analog circuits (low-pass and notch filters), energy storage in switching power supplies, and coupling or tuning circuits. Induction is also the principle behind transformers, where two inductors are magnetically coupled to transfer energy.