Johnson's natural philosophy and key to philosophical charts : illustrated with 500 cuts; being reduced photographic copies of all the diagrams contained in the author's philosophical series of indestructible school charts ; for the use of schools and families (1878)
Place betweenthem an astatic needle (764). If thejunction at R be heated, as by thespirit-lamp, the needle will be de-flected in one direction; if the otherjunction, S, be heated, the needlewill turn in the opposite direction. Thermo-electric currents are de-veloped by unequally heating different… … Fig. 66. 788. Figure 66. —The thermo-electric revolving arch.—A delicatereaction between the magnetism of theeartli and the electric current may be hadby this instrument. The arch is a pieceof brass wire, nicely adjusted on a pivot atthe top of the support, having its two endsconnected to German…
Physics · Astronomy
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