Page:Incandescent electric lighting- A practical description of the Edison system.djvu/20

 to touch each other; this latter being shown in the cut located near the handle on the forward end of the shaft. Figure 3 shows an end view of this insulating device.

. 3.

If the shaft which supports the loop is rapidly revolved; a current of electricity will be set up in the wire loop by bridging over the space at the ends of the wire between the metal plates with a piece of metal or another loop of copper wire; copper always being used to conduct electricity where it can be, for the reason that it is the best practical conductor of electricity.

Such a device as this would be of little service in producing the large currents needed for the electric light, both because there would be an insufficient amount of wire and, further, because such magnets as have been described—called permanent magnets—cannot be made sufficiently strong for the commercial generation of great currents.