A-B-C of Electricity

by Wm. H. Meadowcroft

The picture below will show you the appearance of an incandescent lamp. (Fig. 23.)

Fig. 23

You will see that this lamp consists of a pear-shaped globe, and inside is a long U-shaped strip of carbon no thicker than an ordinary thread. This is a strip of bamboo cane[1] which has been carbonized to a thread of charcoal. It is joined to two wires which come through the glass. These two wires come down through the bottom of the globe, and one is fastened to a brass screw-ring, while the other wire is fastened to a brass button at the bottom of the lamp. These two (the ring and button) must, as you know, be separated from each other by something which will not carry electricity, or they would make a short circuit when the electricity was applied. We separate the ring and the button in various ways.

Now, if we took the ends of two wires which were charged with the proper amount of electricity and put one wire on the screw-ring and the other on the button, the lamp would light up, because there would be a complete path for the current to travel in.

Fig. 24

It will, however, be plain to you that it would be awkward to light the lamps in this way, so we use a "socket" into which the lamp is screwed. (Fig. 24.)

The wires from the dynamo carrying the electricity are connected in the socket, one wire with the screw thread into which the screw-ring fits, and the other with a button which the button on the lamp touches when the lamp is screwed into the socket. Thus we have a connected path for the current to travel in, or, as it is termed, a complete circuit.