. How to make and use electricity ... ne current pro-duced. The electro-motive force varies also with the numberof turns of wire in the coil used, and with the strength of theinducing magnets. The helix around the core may be madeup of many turns of wire, if a high electro-motive force is de-sired to overcome great external resistance; or of fewer turnsof larger wire if a small internal resistance is wanted, as forelectro-plating. When a very intense current is wanted an engine of eight orten horse power is required. By means of the dynamoelectric lighting, which formerly was considered a curi
. How to make and use electricity ... ne current pro-duced. The electro-motive force varies also with the numberof turns of wire in the coil used, and with the strength of theinducing magnets. The helix around the core may be madeup of many turns of wire, if a high electro-motive force is de-sired to overcome great external resistance; or of fewer turnsof larger wire if a small internal resistance is wanted, as forelectro-plating. When a very intense current is wanted an engine of eight orten horse power is required. By means of the dynamoelectric lighting, which formerly was considered a curiosity, hasbeen reduced in expense so as to become a rival of gas lighting. If a core of iron, or still better, a bundle of wire (AA. Fig. 5.)is4 inserted in the primary coil it is evident that it will be mag-netized and demagnetized every time the primary i3 madeand broken. The starting and cessation ot amperian cur-rents in the core in the same direction as the primary current,and simultaneous with the commencement and ending of the. primarycurrent, greatly intensifies the secondary current. Thatis, if a coil of wire is wound around a core of iron andattached to a battery, another coil which is wound aroundthe first in an opposite direction, but having no connection USE ELECTRICITY. 41 with it, will be charged with a greater quantity of electricitythan the first. This is called induction and the coil an induc-tion coil. To save trouble in making and breaking the circuitby in Fig. 5, the core is also utilized in the construction ofan automatic rnake-and-break piece. A soft iron hammer, B.,is connected with the steel spring C, which is in turn connectedwith one of the terminals of the primary wire. The hammerpresses against the point of a screw, D., and thus through thescrew closes the circuit. But when the core becomes magnet-ized the hammer is drawn away from the screw and the circuitis broken. The circuit broken the core loses its magnetism,and the hammer springs back
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectelectricity, bookyear
