An international system of electro-therapeutics : for students, general practitioners, and specialists . Fig. 29.—Coils. varied indefinitely. They are usually made to increase consecutively,as, for example, 1, 2, 5, 10, 20, 50, 100, 500 ohms, and so on. If all the plugs are in their places, there is practically no resistancebetween the terminal binding-screws; but if any of the plugs be takenout, the coil of that section is brought into the circuit. It follows, then,that 133^ withdrawing any or all of the plugs we can introduce less ormore resistance. Numbers representing the various resistanc
An international system of electro-therapeutics : for students, general practitioners, and specialists . Fig. 29.—Coils. varied indefinitely. They are usually made to increase consecutively,as, for example, 1, 2, 5, 10, 20, 50, 100, 500 ohms, and so on. If all the plugs are in their places, there is practically no resistancebetween the terminal binding-screws; but if any of the plugs be takenout, the coil of that section is brought into the circuit. It follows, then,that 133^ withdrawing any or all of the plugs we can introduce less ormore resistance. Numbers representing the various resistances of the coils are usually. Fig. 30.—Standard Box-Rhkostat. placed opposite the holes, and by adding together the numbers unpluggedwe ascertain the total resistance inserted. The wire used in resistance coils is generallj^ made of German silver,because the resistance of that alloy changes very little with variations oftemperature; it is insulated with silk, and always wound double, as GALVANISM. A-235 shown, so as to neutralize any inductive action of the convolutions oneach other, and also to prevent the coils from affecting galvanometersnear them ; when so arranged, the current flows at the same time in twoopposite directions round the spool, effectually preventing any inductivetroubles. It is usual to so arrange the different resistances that, bj^ properlycombining them, any value, from a fraction of an ohm to 10,000 ohms,can be obtained. Those rheostats which are now mostly used by medical men are ofthe wire, the water, and the carbon order. I will describe and illustratethe three different kinds. They all
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectuterus, bookyear1894
