. The Röntgen rays in medical work . rrent motor may be used to drive a directcurrent dynamo. The machines may be coupled by a belt, or theymay be built upon one shaft. In this method there is a conversion of electrical into mechanicalenergy, and a reconversion of mechanical energy into electrical THE ELECTRICAL APPARATUS 61 again. The method allows of a free choice as to the pressureand magnitude of the generated current, within the limits of theenergy expended on the motor side. 2. A mechanical rectifier may be used, and by this is meant aninstrument which periodically makes contacts, closin
. The Röntgen rays in medical work . rrent motor may be used to drive a directcurrent dynamo. The machines may be coupled by a belt, or theymay be built upon one shaft. In this method there is a conversion of electrical into mechanicalenergy, and a reconversion of mechanical energy into electrical THE ELECTRICAL APPARATUS 61 again. The method allows of a free choice as to the pressureand magnitude of the generated current, within the limits of theenergy expended on the motor side. 2. A mechanical rectifier may be used, and by this is meant aninstrument which periodically makes contacts, closing the circuit atsuch intervals of time as to transmit the impulses passing in onedirection, while arresting or diverting those impulses which wouldtend to pass in the opposite direction. A rectifier, therefore, doesnot give a smooth flow of direct current, but a series of distinctimpulses which all pass in the same direction. This may be quiteas useful as a steady current for some purposes, such as the chargingof accumulators. f ■. Fig. 35.—Dr. Battens Rectifier (Read and Gale). There are several rectifiers in use among medical men, thoughnone have come into very extensive use, because of the greaterconvenience of the chemical or electrolytic rectifier, to be describedimmediately. Dr. Battens rectifier consists of a short steel magnet, movingon a pivot between the poles of an electromagnet fed by an alter-nating current. It is attracted by each pole in turn, as the directionof the current changes, and in its excursions it makes contact witheach of two studs, and so closes the circuit of utilization. It is soarranged as to permit of the utilization of both semi-periods of thealternating current, so that, for example, two sets of accumulatorscan be charged simultaneously (Fig. 35). 62 THE BONTGEN BA YS IN MEDICAL WORK A very ingenious detail of Dr. Battens rectifier is the use of atinfoil condenser in the circuit of the electromagnet, and of a self-induction coil in the rect
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