Inductive coupling is the mutual magnetic influence of two or more spatially adjacent electrical circuits by electromagnetic induction as a result of a change in the magnetic flux. Counter-induction is the basis of some technical devices (such as the transformer), but it can also be a very undesirable effect (such as in the field of electromagnetic compatibility). One parameter that describes this effect is counter-inductance: this establishes a relationship between the current flowing in a circuit.
Related coupling types in this context are capacitive coupling, galvanic coupling and radiation coupling. In order to keep the following description as physically general as possible, we will deliberately not talk about coils, but rather about conductor loops in general, which may be shaped as desired and may also protrude into each other. A single conductor loop should be described as an infinitesimally thin line. Thicker wires and coils can be modeled by summing over many such thin individual loops.
In the field of electromagnetic compatibility (EMC), counter-inductance is also referred to as magnetic coupling or inductive coupling and describes a magnetic coupling of adjacent electrical circuits, which is usually undesirable. The magnetic flux caused by the current in an electrical circuit, is an additional induced source voltage, which can occur as an undesirable disturbance in the circuit.
Due to the higher energy density of the magnetic field compared to the electric field, a relatively high power transmission at medium frequencies can also be achieved by means of inductive coupling. This circumstance is the subject of the development of contactless transport systems or contactless charging of the accumulator of vehicles and devices.
In the field of message transmission, inductive coupling is used in the context of inductive transmission, for example in the contactless signal transmission of a sensor signal between the sensor and the display device or contactless chip cards, the so-called RFID (radio-frequency identification) or NFC (near field communication).