. How to make and use electricity ... buttons of carbon; theformer is ^attached to a sounding-board of thin pine wood,well seasoned, the latter to a steel spring C, and both areconnected in circuit with a battery and a telephone, used as areceiver. The spring presses B against A, but any slight jarwill cause a variation of the pressure. The reader must havelearned ere this that the effect of a loose contact between anytwo parts of a circuit is to increase the resistance, and therebyweaken the current; but the effect of a slight variation in pres-sure is especially noticeable wnen eitner or bot
. How to make and use electricity ... buttons of carbon; theformer is ^attached to a sounding-board of thin pine wood,well seasoned, the latter to a steel spring C, and both areconnected in circuit with a battery and a telephone, used as areceiver. The spring presses B against A, but any slight jarwill cause a variation of the pressure. The reader must havelearned ere this that the effect of a loose contact between anytwo parts of a circuit is to increase the resistance, and therebyweaken the current; but the effect of a slight variation in pres-sure is especially noticeable wnen eitner or both of the parts arecarbon. Now any slight jar, as that caused by the tick of awatch, will cause a variation in the pressure between the car-bon buttons, and this will produce a corresponding variationin the current, and the fluctuations in the current are attend-ed with the usual vibrations in the telephone receivei. By means of this instrument, called microphone, any littlesounds, as its name indicates, such as the ticking of a watch. 56 HOW TO MAKE AND or the footfall of an insect, may be reproduced a considerabledistance, and be as audible as though the original sounds weremade close to the ear. If a person talk to the thin pineboard, his words will be distinctly heard in the receiver. The last subject which we will consider is the Storage orSecondary battery. A Storage battery consists simply of two lead plates im-mersed in a solution of sulphuric acid and water (water 10parts, acid 1 part). Figure 5 represents ajar containing theelements ready for use.
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectelectricity, bookyear
