Electricity for public schools and colleges . earth has little (or, strictly,no) action, is called an astatic system ; and a galvanometer inwhich such a system isemployed is called anastatic galTa?ioineter. There are two com-binations that give usconvenient astatic sys-tems. (i.) Let us connectrigidly two needles n sand ?i s of nearly equalstrength, so that, whenthey are suspended,they are in the samevertical plane; the polesbeing directed oppositeways. If Ji s be some-what the stronger, thetwo needles will act icithrespect to the earth asone needle of the samelength /, but of pole-strength me
Electricity for public schools and colleges . earth has little (or, strictly,no) action, is called an astatic system ; and a galvanometer inwhich such a system isemployed is called anastatic galTa?ioineter. There are two com-binations that give usconvenient astatic sys-tems. (i.) Let us connectrigidly two needles n sand ?i s of nearly equalstrength, so that, whenthey are suspended,they are in the samevertical plane; the polesbeing directed oppositeways. If Ji s be some-what the stronger, thetwo needles will act icithrespect to the earth asone needle of the samelength /, but of pole-strength measured bythe difference (« —ju) ;so that the magnetic moment with respect to the earth is /(^t—/t/), and may be verysmall indeed by having the pole-strengths \x and ^i nearly equal. The coils of the galvanometer, however, as seen in the figure,are so arranged that one needle of moment ^( / is in the strongfield within the coil; while the other needle, /*/, inasmuch as itis reversed in direction and is also in the reverse field above the. Fig. 1.
Size: 1320px × 1893px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, bookpubl, booksubjectelectricity
