What is an Inductor?
Inductors are electronic components designed to store magnetic field energy, with the unit of inductance measured in henrys (H). In practical applications, microhenries (µH) and millihenries (mH) are commonly encountered due to the typically large values of the henry. In circuit diagrams, the letter “L” is used to designate an inductor.
The measurement of inductance involves observing the voltage when the current changes in the inductor. Importantly, this induced voltage always opposes the current flow, a phenomenon known as Lenz’s law.
Mutual inductance is defined as the ratio of current in one circuit to the magnetic flux coupled to a second circuit. It is denoted as L12, with the subscripts indicating the two circuits considered. Contrastingly, self-inductance (L11 or simply L) involves the flux in a circuit generated by the current in that same circuit. Both mutual and self-inductance are functions of circuit geometry, and mutual inductance can exist even when no current flows. Mutual inductance can have either polarity and the induced voltage, as per Faraday’s law, can vary in polarity based on the orientation of the coupling loop.
Mutual inductance can be a mechanism for unwanted signal induction into a circuit, and undesired coupling can be mitigated by altering circuit geometry or physically moving the interfering or sensitive circuits. Techniques such as limiting the extent of external flux or adjusting coupling loop areas can be employed to reduce interference.