Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . agnetic instruments, like the galvanic current. Inthe cut, the revolving bell engine (Fig. 147) is shownin connection with the machine. The primary cur-rent is employed, and those instruments are bestsuited to the purpose which do not require a power-24* 282 DAVISS MANUAL ful current to operate them. Both quantity and in-tensity armatures may be adapted to any of themachines, so that one may be substituted for theother at pleasure. 459. We now pass to
Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . agnetic instruments, like the galvanic current. Inthe cut, the revolving bell engine (Fig. 147) is shownin connection with the machine. The primary cur-rent is employed, and those instruments are bestsuited to the purpose which do not require a power-24* 282 DAVISS MANUAL ful current to operate them. Both quantity and in-tensity armatures may be adapted to any of themachines, so that one may be substituted for theother at pleasure. 459. We now pass to a class of instruments inwhich electric currents are induced by electro-mag-nets whose magnetism is alternately acquired andlost. These instruments consist essentially of doublehelices containing bars or wires of soft iron. Themagneto-electric current is thus obtained in con-junction with that excited by electro-dynamic in-duction, and the current formed by their union iscalled a secondary^ though only in part such. 460. Platinum wire may be ignited by this sec-ondary current in the manner represented in Fig. ?ill H II ?**-. Fig, 17a. 178. A short piece of fine platinum wire is securedby binding screws to the wires of a large electro- POWER OF BATTERIES. 283 magnet. The wires are uncovered at that point,and being connected by the platinum, a part of thebattery current passes through it. It should be longenough not to be fully ignited by this one of the wires is connected with one poleof a single pair of Groves battery, and the remainingwire brought in contact with the other pole, theelectro-magnet becomes charged. On breaking con-tact, its magnetism instantly disappears, and a cur-rent is induced in the surrounding coil which floAvsin conjunction with the secondary excited by thebattery current itself The combined currents haveno circuit open to them except through the platinumwire, which is for the moment ignited by theirpassage. 461. Since the description of Sme
Size: 2226px × 1123px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1850, booksubjectmagnetism, bookyear18
