. An elementary manual of radiotelegraphy and radiotelephony for students and operators . andimmediately afterwardsthe galvanouieter cir-cuit is , during a largepart of one revolutionthe iron wire bundlesaie left magnetised andsurrounded by a secon-dary coil connected toa galvanometer. Ifduring this periodelectric oscillationspass through the de-magnetising coils, anelectromotive force isinduced in the secon-dary bobbin by the demagnetisation of the iron, and this causes a deflection of thegalvanometer coil. Since the interrupter discs are rotated veryrapidly, if the oscillation
. An elementary manual of radiotelegraphy and radiotelephony for students and operators . andimmediately afterwardsthe galvanouieter cir-cuit is , during a largepart of one revolutionthe iron wire bundlesaie left magnetised andsurrounded by a secon-dary coil connected toa galvanometer. Ifduring this periodelectric oscillationspass through the de-magnetising coils, anelectromotive force isinduced in the secon-dary bobbin by the demagnetisation of the iron, and this causes a deflection of thegalvanometer coil. Since the interrupter discs are rotated veryrapidly, if the oscillations continue, this intermittent electromotiveforce produces a practically steady current through the galvano-meter which is proportional to the demagnetising force beingapplied to the iron. Hence the arrangement becomes not merelya means of detecting oscillations, but of measuring their instrument has been employed by Buscemi for quantitativemeasurement of the opacity of various dielectrics to electricwaves. The endeavour to account for these interesting magnetic effects. Fig. 9. 2o6 RADIOTELEGRAPHY of electric oscillation has given rise to much research and dis-cussion. The chief contributions to it have come from Maurain,L. H. Walter, Ascoli, Arno, Piola, Foley, C. Tissot, P. Duhem,W. H. Eccles, and J. Eussell. Eussell has carefully distinguished between the two conditionsunder wliich we can work. (i.) Iron or steel may be placed in a constant magnetic field,and then subjected to the action of electric oscillations. (ii.) Iron or steel may be subjected to continuing electricoscillations, and then the magnetic field around it changed. In the case of Eutherfords experiment, hard iron or steelhaving considerable retentivity is subjected to a magnetic force,which is then removed, leaving remanent magnetisation in theiron. The action of oscillations taking place round the iron isthen always to remove or diminish this magnetisation, and thiscan be detected by a change
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecttelegra, bookyear1916
