V.3 No 1

85

Several experiments studying dynamic magnetic field

4.4. Brief theoretical analysis of yielded experimental results

To clear the essence of processes occurring with the induction, consider first the results of experiment at equal voltages across the primary windings and suppose that the combined emf induced in the probe is the sum of emf induced by the sides of each winding parallel to the probe. Then we can simply take the sum of data for emf at U_c = 0  from Table 3. As we revealed before, the case U_c = 0 relates to the induction of winding a in absence of voltage across the winding c and, given the circuit is fully symmetrical at the present statement of problem, we can presume that the pattern of amplitude variation of emf excited by the winding c (in absence of voltage across the winding a) will be similar to the measured values of emf for winding a in absence of voltage across the winding c.

The result of adding, taking into account the direction of momentary currents in primary windings, is shown in Fig. 21.

Fig. 21. Adding of inductive electromotive forces excited in the probe by the sides of primary windings parallel to the leg of probe

We can see from Fig. 21 that when connected in phase, the emfs excited by related sides of windings a and c are subtracted. With it we really yield the inversion of inductive emf at the centre of gap and growth of emf to the boundaries of gap. In the diagram, the emf difference at the boundaries of gap is equal to 0,0325 V. Table 3 gives for this case 0,03 V that is in a good agreement with calculation.

At the anti-phase voltages across the primary windings, we have to add the inductive emfs. According to the right-hand part of diagram, this summation leads to the inductive emf uniform in all the gap, with the amplitude 0,1525 V. For this case, Table 3 gives the same value.

So we have made sure, phenomenology and experiment are in good agreement. An important corollary follows from the above described. Should with the primary windings connected in phase the fall of inductive emf excited in each winding were absent, the resulting emf would be zero. We know, this is the case of bifilar winding.

Seeing so good agreement of patterns and values of studied regularities, let us apply this summation to the case of inequal voltages across the primary windings. For it we have to take into account additionally the variation of phase of induced emf  ₂  which, as we said above, at U_c = 0  varies from - 46,08 to - 34,57 degrees. And just as in previous consideration, we will presume fully identical the emf induced in the probe of each primary winding.