V.3 No 1

75

Several experiments studying dynamic magnetic field

Some other substantiation of the law of EM induction is grounded on the attempt to relate the phenomenology of EM induction with the induction of current in conductors moving in magnetic field. In particular, Tamm [4] substantiates this relation so. "Thus, the value of electromotive force of induction in the loop L₁ has to be determined by the formula

at any even motion of loop L₁ relatively to the current J₂ exciting the field H. We can naturally suppose that this equation remains applicable in case if L₂ moves irregularly (as to the inertial frame). Furthermore, we will suppose (! - authors) that (4) remains true in case if the variation of magnetic flux through the loop L₁ is conditioned not only by the motion of L₁ or motion of loop L₂ carrying the direct current, but also by opening and closing of current in L₂ , by variation of its current J₂ (alternating current) and so on; in other words, we will suppose that (4) is applicable out of dependence on the type of causes conditioning the variation of value of magnetic flux . This supposition well corresponds to the spirit of short-range theory and field theory generally, as it, in essence, reduces to an admission that all electromagnetic phenomena in the given body or in the given region of space are determined by the values of field strength (and its derivatives with respect to time) in this region of space and do not depend at all on the way this field was excited" [4, p. 357].

It follows from the given standard description of process of inter-induction of loops that:

1. in the existent treatments the flux variations are connected directly with the variations of current in the primary loop without change of the field structure in transition from stationary processes to those dynamic;

2. the direction of induced electromotive force (emf) is vectorially related to the direction of flux of vector B threading the secondary loop.

Relying on these conclusions, let us consider the model of air-core transformer with two secondary loops C₂'   and C₂''   located in one plane with the primary loop C₁   , as it is shown in Fig. 4.

Fig. 4. Model of the air-core transformer with two secondary loops and the pattern of force lines of alternating magnetic field in the given model

We can see from construction, if we base on the principle of closed lines of force of dynamic magnetic field, those for the exterior and interior secondary loops are directed oppositely. With it are absent any closures of field typical for transformers with ferromagnetic cores which could distort the pattern of lines of force. Thus, if the conventional treatment of induction process is true, the phase shift between the emf induced in the interior and exterior secondary loops has to be equal to 180 degrees. Simply speaking, the electromotive forces (emfs) in these loops have to be in anti-phase. This peculiarity is quite checkable experimentally.