Electrical measurementsA laboratory manual . ., being proportional to the cur-rents, are also proportional to the corresponding deflec-tions. ohms : R = 15,000 ohms. Cell. Deflection. Daniell, 64 volts. Diamond Carbon, 67 Gassner Dry Cell, 75 Ajax Dry Cell, 63 The Daniell cell was freshly set up, but the others were oldcells. 90. The Condenser Method of comparing — Let (x be a sensitive galvanometer with a small damp-ing coefficient. Connect with the condenser 0 and thebattery B by means of a charge and discharge key ^(Fig. 88). The con-denser
Electrical measurementsA laboratory manual . ., being proportional to the cur-rents, are also proportional to the corresponding deflec-tions. ohms : R = 15,000 ohms. Cell. Deflection. Daniell, 64 volts. Diamond Carbon, 67 Gassner Dry Cell, 75 Ajax Dry Cell, 63 The Daniell cell was freshly set up, but the others were oldcells. 90. The Condenser Method of comparing — Let (x be a sensitive galvanometer with a small damp-ing coefficient. Connect with the condenser 0 and thebattery B by means of a charge and discharge key ^(Fig. 88). The con-denser will need to havea capacity of from of a the first swingseveral times Avhen thecondenser is dischargedthrough the galvanom-eter and take the meanfor d^. The complete pe-riod of swing of the gal-vanometer, for convenience in reading, should be from5 to 10 seconds. Next repeat the observations with asecond battery and let the mean of the deflections be c?2 •Then if Ei and E. are the of the two cells,. MEASUBEMENT OF ELECTJiOMOTITE FORCE. 189 To save time in waiting for the galvanometer needleto come to rest after each observation, a small coil maybe placed near the needle, and a single cell may be con-nected in circuit with it. By tapping the key in thiscontrol circuit at the proper moment the needle may bequickly brought to rest. If the ballistic form of the dArsonval galvanometerbe used, the motion of the coil may be arrested by short-circuiting the galvanometer by means of an extra keyfor the purpose. In this method the first swing of the needle from restis nearly proportional to the quantity of electricity dis-charged through the galvanometer; and, since the capacityof the condenser remains unchanged, the quantities areproportional to the charging the condenser. Ifinstead of a change in electromotive force another con-denser of different capacity be used, the deflections d^and do will be proportional to the capacities of the
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Keywords: ., bookcentury1800, bookdecade1890, bookpublisherbosto, bookyear1895
