FIG. 31. Independent Interrupter.
The Mercury Turbine form of interrupter is a very unsuccessful type in which a stream of mercury is made to play against a number of saw-shaped metal teeth. A spiral worm terminating in a nozzle-at the top is rapidly revolved by an electric motor. The lower end of the tubular worm dips into a mercury reservoir so that when the spiral is revolved, the mercury rises in the tube by centrifugal action and is thrown out from the upper end in the form of a jet.
When the revolving jet strikes one of the metal teeth the circuit is made and when it passes between it is broken. Raising and lowering the saw teeth so that the mercury strikes either the lower or upper part varies the ratio of time of the make and break.
FIG. 32. Electrolytic Interrupter.
The electrolytic interrupter consists of a cathode or negative electrode of sheet lead immersed in diluted sulphuric acid and an anode composed of a piece of platinum wire placed in a porcelain tube and projecting through a small hole in the bottom, so that only a very small portion of the wire is exposed to contact with the liquid. When a strong electric current is passed through the acid electrolyte, the current is very rapidly interrupted by the formation of gases on the small platinum electrode. The number of breaks per second possible with an electrolytic interrupter is extremely high. A potential of at least 40 volts is required to operate such an interrupter, however.
LESSON FIFTEEN. THE HIGH POTENTIAL TRANSFORMER.
The transformer, like the induction coil, steps up the voltage of the current to a value where it is sufficient to charge the condenser.
The transformer for wireless work should have a potential of from 15,000 to 40,000 volts. Several manufacturers claim advantage for low voltages and build machines having a potential of only about 8,000 volts, but experiments have shown that under most ordinary conditions higher voltages permit greater range of transmission.
Both open and closed core machines may be used with good results. Probably, however, neither one is the best.