V.4 No 1

85

Study of electromotive force induced by heterogeneous magnetic field

The diagram of emf induced in the secondary loop with respect to the loop size and frequency of current in the primary winding, which was plotted on the basis of values shown in Table 2, is shown in different views in Fig. 13.

Fig. 13. The diagram of variation of emf induced in the secondary loop dependently on the frequency f of current in the primary winding and on the distance h from the outer side of secondary loop to the core

We see from the Table 2 and Fig. 13 that, just as in the first experiment, in the region 170 kHz there is an extreme of emf. But in distinct from the first experiment, the emf varies in much more complicated way, and the resonances are revealed not at one frequency but at the band 120 kHz to 200 kHz. This is because in the second experiment we do not retain the geometry of secondary loop. So the maximum of emf can appear not only with fully moved aside from the core outer side of the loop, but also at its intermediate positions - and we see it at the frequencies 120- 200 kHz. It is well seen in the table, how the maximum of amplitude gradually shifts from small to large values h, which corresponds to the growing area of the loop and, as relates, to growing inductance and, consequently, to the fall of resonance frequency. Especially interesting are the measured data at 120 and 140 kHz. These are the boundary frequencies at which simultaneously reveal both the resonance properties of loop and the dependence of emf on the distance h from the outer side of secondary loop to the core. Due to this, the dependencies of emf on h have minimums shifting as the frequency falls towards larger h, just as the maximums of above analysed resonances. In Fig. 14 we show separately the plot corresponding to the boundary frequency 120 kHz.

Fig. 14. Induction emf in the secondary loop against the distance h from outer side of secondary loop to the core at the frequency in the primary loop f = 120 kHz

We see in this plot that when f changed from zero to 2 cm, the emf amplitude in the secondary loop falls, and at larger distances from the outer side of loop to the core the amplitude grows after the regularity typical for resonance curves. This evidences that when we move the outer side of loop away from core, the very process of induction decreases, though the area of secondary loop grows, and the quantity of force lines crossing the loop also grows. Thus, with this curve we already can judge that Faraday, not Maxwell formulation of induction law is true, and the further study will only corroborate this conclusion.