A refrigerator magnet or fridge magnet is an ornament, often whimsical, attached to a small magnet, which is used to post items such as shopping lists, child art or reminders on a refrigerator door, or which simply serves as decoration. Refrigerator magnets come in a wide variety of shapes and sizes, and may have promotional messages placed on them. Refrigerator magnets are popular souvenir and collectible objects.
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Manufacture
The first fridge magnets were cylindrical or solid rectangular magnets. Later, a flexible magnet was developed, composed of a high-coercivity ferromagnetic compound (usually ferric oxide) mixed with a plastic binder. This is extruded as a sheet and passes on a conveyor belt over a line of powerful cylindrical permanent magnets. These magnets are arranged in a stack with alternating magnetic poles facing up (N, S, N, S,...) on a freely rotating shaft. This impresses the plastic sheet with the magnetic poles in an alternating line format. No electromagnetism is used to generate the magnets. The pole-pole distance is on the order of 5 mm, but varies with manufacturer. Ferrite magnets are commonly used, too, with decorative elements attached to the magnets with adhesive. They were created in the 1920s.
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Magnetic polarization
Unlike most conventional magnets that have distinct north and south poles, flat refrigerator magnets are magnetized during manufacture with alternating north and south poles on the refrigerator side. This can be felt by taking two similar (or identical) refrigerator magnets and sliding them against each other with the "magnetic" sides facing each other: the magnets will alternately repel and attract as they are moved a few millimeters. One can note that magnetic field outside a uniformly magnetized thin sheet is actually zero, neglecting the edge effects (see, for instance, D. Budker and A. Sushkov, Physics in Your Feet", OUP, 2015), so a uniformly magnetized magnet does not stick to a refrigerator. Most magnets have a special, slightly more sophisticated magnetization pattern called a Halbach array. This construction gives enhanced magnetic field on one side and almost zero magnetic field on the other.
Types
Plastic letters attached to small, thick rectangular magnets have been manufactured since the 1960s, and marketed as an educational product for young children. In the 1990s, Magnetic Poetry--sets of small sheet magnets printed with individual words--became popular; these sets are used to create sentences including poetry. Magnets may be attached to souvenir objects, or to practical objects such as hooks, notepads, etc.
Collecting
Collecting magnets is a hobby, with some collectors specializing in magnets from their travels, or of a particular theme. They are sold at souvenir shops worldwide. There is no generally recognized term (e.g. numismatics for currency collecting) for magnet collecting. A Russian collector has proposed the term memomagnetics (Russian: ?????????????), derived from the words memoriale (Latin) and magnetis (Greek) A collector of magnets would be called memomagnetist. These terms have been used by at least one Russian online community for magnet collectors.
Large collections
At one time, the largest verified collection of refrigerator magnets belonged to Louise J. Greenfarb from Henderson, Nevada (suburb of Las Vegas, United States). Her world record was included to the Guinness World Records with 19,300 items as of 1997. According to the British "Book of alternative records", it grew to 29,000 as of February 2002, and later up to over 30,000 items. Over 7,000 magnets from Greenfarb's collection were exhibited at the Guinness Museum in Las Vegas, which has since closed. According to her son, Bryan Greenfarb, as of November 2015 Louise still collects and has around 45,000 plus non-duplicate refrigerator magnets but the Guinness verification process, which can take over 6 plus months, is just too taxing to keep validating the exact number.
In January 1999, Tony Lloyd, a teacher in Cardiff, Wales, was interviewed by the Channel 4 Television programme Collector's Lot when it was ascertained that he had largest collection of fridge magnets in Europe at that time, over 2000. As of June 2014, he had a collection of over 4,000.
Home crafts
Refrigerator magnets are also popular as crafts projects.
Source of the article : Wikipedia
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