If you wind the wire around a small paper tube into which a nail will slide easily, the coil will draw the nail in when the current is turned On. A hollow coil of this sort is called a solenoid.
Electro-magnets and solenoids play a part in the construction of almost all electrical machinery. They form the essential parts of dynamos, motors, telephone receivers, telegraph relays and sounders, and a host of other devices.
The form usually given to an electro-magnet depends upon the use to which it is to be put. The horseshoe is the most common. This consists of two electro-magnets mounted on a yoke and connected so that the two free poles are North and South.
Fig. 85.—If you wind the Wire around a small Paper Tube into which a Nail will slide easily, the Coil will draw the Nail in when the Current is turned on.
Electro-magnets are made on a huge scale for lifting large castings and heavy pieces of iron. Such magnets are used in the great steel mills and in factories where nails, bolts, etc., are manufactured.
Monster electro-magnets can be seen in wonderful perfection at the great steel mill at Gary, Indiana.
Ships bring the ore down the lakes to Gary, where great steel jaws lift it out of the hold of the boat and carry it to the furnaces.
After being melted, great machines pour it out. It is divided into huge ingots, and these, while hot, are carried to the first part of the rolling mill.
The ingot is squeezed by a machine, made longer and narrower, then squeezed again and made still longer and narrower.