A bar magnet is a rectangular and narrow piece of ferromagnetic material or composite that is capable of generating a magnetic field. The term "ferrous" means "containing iron." Most ferrous metals are magnetic, but not exclusively. Bar magnets feature a uniform and smooth cross section and surface, and are typically made from steel, iron, clay, aluminum, nickel, or cobalt. Bar magnets can retain their magnetism on their own for a long period of time, even when an electric current is not present. In fact, they do not require a consistent electric current to perform their function at all. Therefore, bar magnets are known as permanent magnets, since they can remain magnetized independently. The primary feature of a bar magnet is a north and south pole on opposite ends.
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The History of Bar Magnets
Magnets were first used by the ancient Greeks as early as 600 B.C., after it was discovered that certain objects were drawn toward a magnetic stone. During the Middle Ages, this magnetic stone became known as lodestone. Today, magnets can be found in a vast range of configurations, such as rods, arcs, blocks, rings, and discs.
Applications and Materials of Bar Magnets
The applications for which magnets can be used vary just as much, if not more. They can be used for material handling, sensing, retrieving, separating, holding, and lifting. Magnets can also be made from neodymium, ceramic, samarium cobalt, and alnico. Neodymium magnets are composed of neodymium, iron, boron, and several transition metals, and are incredibly strong. Ceramic magnets are made up of iron oxide and strontium carbonate, and can be used in speakers and DC brushless motors. Samarium cobalt magnets are composed of cobalt, samarium, and iron. They are also very strong and are used as sensors or computer disk drives. Alnico magnets are primarily made from copper, iron, cobalt, nickel, aluminum, and sometimes titanium. They can be sintered or cast, and are utilized as guitar pickups, security systems, electron tubes, and generators.
Functions of Bar Magnets
Out of all the configurations of a magnet, bar magnets are the most commonly used. Their main function is to pick up small metallic objects, like screws or nails. In the realm of industrial manufacturing, magnets can be found in factories, attached to small devices and large cranes in order to pick up metallic shavings left over from metal working processes. When a metallic substance comes into contact with a magnet, the metal is instantly pulled toward it, making a magnet a perfect device to assist in safe and proper disposal of metal shavings and maintaining the cleanliness of a facility. Outside of a factory setting, magnets can be found in countless items, including cabinets, whiteboards, name tag holders, and purses. Bar magnets are the magnets of choice for schools across the world to demonstrate magnetic fields and forces in science classrooms.
- Bar Magnets in Compasses
- While this is the most obvious of a bar magnet’s functions, they can also repel other magnetic alloys, including cobalt, nickel, some rare earth metals and their alloys, and natural minerals like lodestone. Bar magnets can also be used in laboratory applications as magnetic stirring rods, holding cutlery in a safe and organized place within a restaurant, or hanging pictures and receipts on the outside of a home refrigerator. However, the most common application of a bar magnet is the needle in a compass. A bar magnet will always position itself so that its north pole points toward Earth’s north pole. Therefore, a needle in a compass will accurately indicate the direction a traveler is headed. If the north end of a magnet is placed by the south pole of another magnet, the magnets will detract from each other.
- On either side of a bar magnet, the magnetic lines form closed and continuous lines. These lines always flow from north to south and always remain parallel to each other. If a bar magnet is cut in half, it will automatically form into two separate magnets, each with a magnetic field and a set of poles. On average, the magnitude of magnetization is 100,000 A/m. However, this magnitude may vary based on the ferromagnetic material that the magnet is made of. The magnitude of magnetism also depends on the strength of the magnet’s poles and their distance from each other.
Things to Consider When Using Bar Magnets
In using a bar magnet in a home setting, it is imperative that you keep it away from any electronic device such as radios, televisions, and speakers. Even if the magnet has a weak magnetic force, it can cause irreversible damage to a device’s data storage if it comes into contact with it.