. Dental electro-therapeutics. e charged for 10 hours at \ ampere. If continuous main current for lighting purposes is avail-able it is far easier and cheaper to recharge accumulatorsfrom this source, provided the voltage of the main approxi-mates to that of the accumulators or that suitable meansbe taken to reduce it. In recharging accumulators the capacity of the cellsshould be taken into account and the charging current SECONDARY BATTERIES OR ACCUMULATORS 63 measured with an amperemeter and calculated in ampere-hours to correspond with the capacity of the cells; therate of charging should n
. Dental electro-therapeutics. e charged for 10 hours at \ ampere. If continuous main current for lighting purposes is avail-able it is far easier and cheaper to recharge accumulatorsfrom this source, provided the voltage of the main approxi-mates to that of the accumulators or that suitable meansbe taken to reduce it. In recharging accumulators the capacity of the cellsshould be taken into account and the charging current SECONDARY BATTERIES OR ACCUMULATORS 63 measured with an amperemeter and calculated in ampere-hours to correspond with the capacity of the cells; therate of charging should not be too rapid; the most efficientrate being usually marked by the makers, and is usuallyabout one-tenth the capacity. Those accustomed to therecharging of accumulators can determine when fullycharged by the sound of effervescence of gases in the elec-trolyte of the cells, when they are only partly charged slighteffervescence is audible, and when fully charged a distinctnoise of active effervescence is heard within the Fig. 12.—Resistance lamps. In charging from the main, the correct poles of bothsource of current and battery must be determined, thiscan be carried out by methods already described (p. 42).The like poles of both are connected and a resistance, theamount of which is determined by the current required,is placed in circuit between the negative pole of the batteryand negative of the current supply. The current is passedfrom the positive pole of the main to the positive terminal 64 CELLS of the accumulators, through the plates and electrolytewithin the cells and out at the negative terminal, andthrough the resistance; carbon-filament lamps of differentpowers are often used as a cheap and convenient form ofresistance, several usually being employed in parallel. The accumulator is useful for heating a cautery loopand for lighting mouth lamps. It has a very useful placein the surgery, especially where the current is not availablefrom a dynamo source. The batte
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