curl07

V.2 No 2	7
Theorem of curl of a potential vector


To corroborate this theoretical concept, we have carried out the experiment on radiation/receipt of transversal acoustic wave in gas medium [12]. We intentionally used the standard technique of studying the polarised EM microwaves described, e.g., by Kalitievsky [13, pp.23-24]. The block-diagram of the setup is presented in Fig. 5. It consisted of the sound-frequency generator 1, the radiator 2 designed for this experiment, and the receiver of transversal acoustic wave 3 which was fully similar to the radiator (they were constructed after balance scheme, compensating the parasitic longitudinal component), the received signal amplifier 5 and registering oscillograph 6. Both radiator and receiver were placed into the screening trumpets 4. Furthermore, the radiator was able to turn in the vertical plane, producing the angle between the polarisation planes of radiator and receiver. The working frequency was 7,4 kHz.

The fact of radiation/receipt of transversal acoustic wave is corroborated by the polar diagrams of amplitude A_m and phase _m of the received signal dependently on the angle between the polarisation planes of radiator and receiver (see Fig. 6). They were picked for the near (r = 99 mm) and far (r = 620 mm) fields. In both sets of measurement the amplitude variation of received signal with turning the radiator by 90 and the phase inversion of received signal with turning the radiator by 180 are clearly seen.

In Fig. 7 we presented the experimental dependencies of amplitude A_m (Fig. 7 a), of the delay phases of wave process _m (Fig. 7 b) and of phase velocity of wave propagation v_f (Fig. 7 c) on the distance r. The near field extending in this experiment up to 320 mm is characterised by the fast amplitude decrease and the fast-growing phase delay with the low velocity of wave propagation. In this region the wave amplitude vanishes periodically, and at these points (shown by the dotted line in Fig. 7b) the signal phase changes abruptly by 180 - i.e., in fact the signal inversion occurs and masks the progressive pattern of process in this region by the outward appearance of standing wave. None the less, if we did not take into account this inversion in calculations, then _m varies with the distance quite smoothly and faster than in the far field. As transiting to the far field, the amplitude attenuation with the distance decreases, the phase inversions cease and the wave propagation velocity stabilises at the value close to that classical - 326 m/s. The wave propagation pattern transformations, with remaining the polarisation plane, evidence that in the far field the transversal acoustic wave in gas has formed. This completely corroborates the theoretical concept stated above.