High frequency currents : their production, physical properties, physiological effects, and therapeutical uses / by H. Evelyn Crook.

  • Crook, H. Evelyn (Herbert Evelyn)
Date:
1909
Catalogue details

Licence: Public Domain Mark

Credit: High frequency currents : their production, physical properties, physiological effects, and therapeutical uses / by H. Evelyn Crook. Source: Wellcome Collection.

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    mounted upon a suitable board. It is, of course, necessary to take great care that the charging current is connected in such a way that it flows through the lamps to the positive pole of the accumulator, through the cells, and then by the negative pole back to the main. A fully- charged cell has an electromotive force or pressure of 2°5 volts; when the voltage falls below 1°8 volts the cells should be immediately recharged, otherwise the plates will become buckled and the cell rendered useless. If a series of accumulator cells be not in constant use, it is necessary to recharge them from time to time, usually about once a month, so that they may be kept in good order, as, if they are allowed to run down by leakage, a sulphate of lead in a crystalline form is hable to become deposited upon the plates; this salt is insoluble, and will so increase the internal resistance, and thereby decrease the storage capacity, that the cells will be speedily ruined. A convenient size of accumulator for high frequency work consists of six cells, which yield a pressure of 12 volts. Accumulators are now made in a very much more convenient and portable form than some few years ago. This is a very important consideration if they have to be taken any distance for the purpose of recharging. The advent of the motor-car and the necessity for portable cells have been mainly responsible for this, and it is now possible to obtain from many of the leading accumu- lator manufacturers a very neat and compact form of accumulator, consisting of transparent celluloid cells enclosed in a teak case, which may be readily carried about by means of a leather handle provided for that
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