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Radio Broadcast
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FIG. 13
Gas tube rectifier
are attracted in this direction. They attain such a speed that, in passing through the gas with which the tube is filled, they collide with its molecules, actually breaking them apart and setting free additional electrons. The final result is the existence of a large number of electrons, all of which will be attracted to the anode of the tube. Now these electrons really are electricity in motion and they thus serve to carry current across the space in the tube. As the conventional way of assuming the current flow is from the positive to the negative side of a battery, and as these electrons travel
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f//amenf m'/7c//f?g Bulb FIG. 14
A schematic diagram of a gas-filled charger
from the negative to the positive electrode of the tube, it is customary to say that the current flows in opposite direction to that of the electron flow.
If an attempt should be made to reverse the current flow by making the cold electrode negative and the filament positive, none of the negative electrons can leave the filament because they are highly attracted to the filament by virtue of the positive charge and are furthermore repelled by the cold electrode on account of its negative charge.
it at once becomes apparent, therefore, that current will pass in one direction only through a tube of this form, and it becomes worthy of
consideration in charging a storage battery from alternating current.
The schematic connections of a rectifier using a gas tube is shown in Fig. 14. As the voltage of the supply is generally considerably above even the voltage of the plate battery, a transformer is used to reduce the voltage economically. Two secondary windings are placed on the transformer, one carrying the actual battery charging current, and one simply for heating the filament.
IIOV.A.C.
FIG. 15
Using both sides of the A.C. is made possible with this arrangement
With the connections shown, the filament will burn to incandescence as soon as the current is turned on. Now, if the battery to be charged is connected as shown, it will receive a pulsating charge every time the secondary alternating current is in a direction in which the tube will allow it to pass. On the reversal, the tube will not allow passage of current. The graph of the charging current will be practically identical with that shown in Fig. 1 1.
Rectifier tubes can also be arranged for charging from both halves of the cycle as shown in Fig. 15. The filament heating connections
FIG. 16
Gas tube rectifier with cover removed