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MANAGERS AND PROJECTIONISTS
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The pressure in pipe A we will assume to be 110 pounds. If we open valve C, its full capacity will flow from pipe A into pipe B, and be used by the motor. Under this condition that is all the water the pressure in pipe A will be able to force through pipe C into pipe B. If pipe C were the only connection between pipes A and B, then the capacity of pipe C would be all the water which could possibly reach the motor.
In addition to pipe C, there is, however, pipe D. We open its valve and instantly the amount of water flowing into pipe B is doubled; also the power of the motor is doubled.
Precisely what water does in Fig. 135 the electric current does in a multiple rheostat connection.
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Figure 136.
In Fig. 136 we have precisely the same thing as applied to electrics. A and B are the wires of a projection circuit, C-D two rheostats and E-F two single pole knife switches. It requires no large understanding to see that if we close switch E the arc will receive amperage equally to the capacity of rheostat C. If we then close switch F the arc will in addition receive the capacity of rheostat D. This is what is known as a "multiple connection," which is again diagrammatically represented in Fig. 137, in which the connection is shown in two ways, the 25 ampere dotted line in A representing the resistance of the coils or grids. If you will carefully trace out the connections in diagrams A and B Fig. 137 you will find they represent precisely the same thing as the water pipe connection in Fig. 135 and the connection shown in Fig. 136.
Any number of rheostats of different type or different voltage may be connected in series, provided the total resistance of the whole be sufficient to reduce the current flow to a point where neither wires or resistance will be overloaded.
Any number of rheostats may be connected in multiple,