Electricity 221 



froni one end of the wire through the brass or copper to 

 which the wire is screwed, through the switch and on out 

 into the end of the next piece of wire. Turn the first switch 

 off and see how a partition of air is made between the place 

 where the electricity conies in and the place where it would 

 get out if it could. Turn the switch on and notice how this 

 gives the electricity a complete path through to the next 

 piece of wire. In this way follow the circuit on through all 

 the switches to the electric lamp. 



If you examine the socket into which the lamp screws 

 and examine the lamp itself, you will see that electricity 

 which goes to the outer part of the socket passes into the 

 rim of the lamp ; from here it goes into one end of the 

 filament. It passes through the filament to the other 

 end, which is connected to the little brass disk at the 

 end of the lamp. From this you can see that it goes 

 into the center point of the socket, and then on into the 

 second wire that connects to the socket. Trace the 

 current on back through this other wire until you see 

 where this wire leads toward the dynamo. You should 

 understand that the electric lamp, the switches, the 

 fuses, all things along the circuit, are simply parts of 

 the long loop from the dynamo, as shown in Figure 

 124. 



Connecting in parallel. The trouble with Figure 

 124 is that it is a little too simple. From looking at 

 it you might think that the loop entered only one build- 

 ing. And it might seem that turning off one switch 

 would shut off the electricity all along the line. It would, 

 too, if the circuit were arranged exactly as shown above. 

 To avoid this, and for other reasons, the main loop from 

 the dynamo has branches so that the electricity can go 



