What is mutual induction?

The phenomenon of mutual induction is at the heart of many electrical appliances. It is not uncommon for a person to face their manifestations in private life, but he does not even suspect it. Let's recall the recent past, when the main means of transmitting information were analog signals. And now, almost all electronic technology is translated into digital modes of modulation. Everyone knows that the "figure" is better. But you wondered what exactly? Surely, some houses still have a wired telephone, served by an analog automatic telephone exchange. If you compare the modern "mobile phones" and "old men", then the comparison is clearly not in favor of the latter. To hear on the background of their conversation intermittent broadcasting or, what is still "better", the words of someone else's communication - this is no surprise. This is because in the telephone cable all the wires are close to each other, so there is mutual induction in the two lines. Another example is the pulsating clicks that appear in the dynamics of the TV or computer speakers when a cell phone is nearby and a bell rings. Finally, the old IDE-trains with 80 conductors used only half of them, and the other 40 prevented the consequences that mutual induction carries. There are many examples, it makes no sense to bring everything together. It is important only to remember that in this case, any "guidance" is and is a mutual induction.

In general, this term means the process of the appearance of an electromotive force (EMF) in one of the adjacent conductors at a time when the current value of the current changes in the other. The simplest mutual induction is explained by a transformer. In a simplified form (a special case), the transformer is two coils wound on the same magnetic circuit. When a current passes through a wire of one of them, a magnetic field arises around it . As a consequence, the magnetic flux that emerges permeates the conductor of the second coil, creating an EMF in it. In order for the induced current to appear, it is sufficient to close the terminals of this coil by creating a chain. As the intensity of the magnetic flux increases, so does mutual induction. To achieve the required characteristics (for example, efficiency), different solutions are used: change the configuration of the magnetic circuit; The winding of coils is performed in a special way, etc. The mutual inductance is measured by means of variometers.

How does it manifest itself in the examples indicated at the beginning of the article? It is very simple: in almost all cases (except for the mobile phone) several conductors are located nearby, at least one of which is electrically conductive. Consequently, a magnetic field arises that generates a magnetic flux. The latter, penetrating the nearby conductors, induces EMF in them, and since the circuit is, then, according to the law of electromagnetic induction, a current appears. Its direction is determined by applying the Lenz rule.

Mutual induction has found wide application in modern electrical engineering. Since some of its undesirable manifestations were mentioned at the beginning of the article, it makes sense to give examples of useful ones. One of the most famous devices is a household voltage regulator. Inside is a transformer (usually a toroidal type) with many leads, each of which corresponds to a certain voltage value. Also in some devices you can find an interesting solution - galvanic isolation. In fact, it is the same transformer (sometimes an optocoupler pair), but not using a transformation ratio. As a result, it is possible to connect several circuits through a magnetic flux, ensuring the proper level of electrical safety. In production, for example, it is a crane-beam.