The magnetic compass is the most familiar compass type. It functions as a pointer to "magnetic north", the local magnetic meridian, because the magnetized needle at its heart aligns itself with the horizontal component of the Earth's magnetic field. The magnetic field exerts a torque on the needle, pulling the North end or pole of the needle approximately toward the Earth's North magnetic pole, and pulling the other toward the Earth's South magnetic pole.^[8] The needle is mounted on a low-friction pivot point, in better compasses a jewel bearing, so it can turn easily. When the compass is held level, the needle turns until, after a few seconds to allow oscillations to die out, it settles into its equilibrium orientation.

In navigation, directions on maps are usually expressed with reference to geographical or true north, the direction toward the Geographical North Pole, the rotation axis of the Earth. Depending on where the compass is located on the surface of the Earth the angle between true north and magnetic north, called magnetic declination can vary widely with geographic location. The local magnetic declination is given on most maps, to allow the map to be oriented with a compass parallel to true north. The location of the Earth's magnetic poles slowly change with time, which is referred to as geomagnetic secular variation. The effect of this means a map with the latest declination information should be used.^[9] Some magnetic compasses include means to manually compensate for the magnetic declination, so that the compass shows true directions. 

Magnets are found in some commonly used medical equipment such as and Magnetic Resonance Imaging machines. MRIs use powerful magnetic fields to generate a radar-like radio signal from inside the body, using the signal to create a clear, detailed picture of bones, organs and other tissue. An MRI magnet is very strong – thousands of times more powerful than common kitchen magnets. Another medical use for magnets is for treating cancer. A doctor injects a magnetically-sensitive fluid into the cancer area and uses a powerful magnet to generate heat in the body. The heat kills the cancer cells without harming healthy organs.
Kavan Yeo(15)

The ­stripe on the back of a credit card is a magnetic stripe, often called a magstripe. The magstripe is made up of tiny iron-based magnetic particles in a plastic-like film. Each particle is really a very tiny bar magnet about 20 millionths of an inch long.

Your card also has a magstripe on the back and a place for your all-important signature.

The magstripe can be "written" because the tiny bar magnets can be magnetized in either a north or south pole direction. The magstripe on the back of the card is very similar to a piece of cassette tape fastened to the back of a card. 
kavan yeo[15]

Neodymium magnet spheres constructed in the shape of a cube

Neodymium magnet spheres used to form different shapes

"Bucky Ball" toy neodymium magnet spheres in close-up

Neodymium magnets, usually small spheres, have been manufactured as educational toys, stress relief products, and an artistic medium. 
kavan yeo[15]

Manufacture[edit]

retail display of magnets

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.^[4] 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. Ferritemagnets are commonly used, too, with decorative elements attached to the magnets with adhesive. They were created in the 1920s.^[5]

Magnetic polarization[edit]

Halbach array polarisation

Magnetic viewing film showing magnetic poles of a fridge magnet

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.^[6] 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.

Alphabetical refrigerator magnets

Magnetic poetry about a domestic cat

Collecting[edit]

Collecting magnets is a hobby, with some collectors specializing in magnets from their travels, or of a particular theme.^[7] 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: мемомагнетика), derived from the words memoriale (Latin) and magnetis (Greek)^[8] A collector of magnets would be called memomagnetist. These terms have been used by at least one Russian online community for magnet collectors.^[9]

According to Collector's Lot magazine, in March 1999, Tony Lloyd of Cardiff, Wales, coined the term "thuramgist" for a "collector of fridge magnets".

Large collections[edit]

Fridge Magnets on a board - Private Collection

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.^[10] 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.^[11] 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.^[12] As of January 2016 he had a collection of over 4500. He was again interviewed by the BBC and ITV during 2017. In February 2018, whilst on holiday in Sri Lanka, his 104th country, Tony's collection surpassed 5,000 magnets. 
kavan yeo [15]

Magna Doodle is a magnetic drawing toy, consisting of a drawing board, a magnetic stylus, and a few magnet shapes. Invented in 1974, over forty million units have been sold to date worldwide, under several brands, product names and variations.^{[citation needed]}

The key element of the toy is the magnetophoretic display panel, filled with a thick, opaque white liquid containing tiny dark magnetic particles. These particles can be drawn to the drawing surface by a magnet-tipped stylus or optionally-provided shapes, or removed to the hidden back side by a sliding eraser bar. The middle layer is divided into a honeycomb of cells, keeping the liquid static and the particles evenly distributed across the panel. The liquid is formulated so that the floating particles can be pulled through it in response to the magnetic forces, but not due to gravity.^[1]

The toy was originally produced as "Magna Doodle" by Tyco until 1997, when Tyco was purchased by Mattel. Mattel then sold the toy under its Fisher-Price brand. The brand was later sold to the Ohio Art Company. Today, the "Magna Doodle" brand is owned by Cra-Z-Art. Fisher-Price have produced their own alternative called the Doodle Pro, while Ohio Art produced the similar Doodle Sketch until 2016 when it sold the brand to Spin Master. The Doodle Pro is still available in the UK from the distribution company Megatel LTD.

Because the Magna Doodle uses no ink or graphite, scuba instructors use it as an underwater whiteboard when instructing students, and divers who wish to pass short notes.^{[citation needed]} The Magna Doodle is not specifically designed to work underwater and many of its components can rust or otherwise deteriorate over time.

In popular culture[edit]

In the TV comedy Friends, a Magna Doodle is visible in Joey and Chandler's apartment, with various messages written on it throughout the series, referencing plot points, current events, inside crew jokes, or just random drawings.^[2]

A version of the Magna Doodle was used in the 1990s Game Show Nick Arcade during their "Video Challenge" games.

kavan yeo[15]
 

kavan yeo[15]

While a magnet isn’t going to wipe your hard drive, if you leave a powerful magnet directly on top of your hard drive there is a slight chance that it could cause damage to the hard drive itself while it’s functioning. The easy solution: don’t put a magnet directly on top of your hard drive during use. By doing that, you can be confident that your hard drive, and the information stored on it, is completely safe.
Germaine Ng (30)

Many computers use magnets to store data on hard drives. Magnets alter the direction of a magnetic material on a hard disk in segments that then represent computer data. Later, computers read the direction of each segment of magnetic material to "read" the data. The small speakers found in computers, televisions and radios also use magnets; inside the speaker, a wire coil and magnet converts electronic signals into sound vibrations.

Electric Power and Other Industries

Magnets offer many benefits to the industrial world. Magnets in electric generators turn mechanical energy into electricity, while some motors use magnets to convert electricity back into mechanical work. In recycling, electrically-powered magnets in cranes grab and move large pieces of metal, some weighing thousands of pounds. Mines use magnetic sorting machines to separate useful metallic ores from crushed rock. In food processing, magnets remove small metal bits from grains and other food. Farmers use magnets to catch pieces of metal that cows eat out in the field. The cow swallows the magnet with its food; as it moves through the animal’s digestive system it traps metal fragments.

Health and Medicine

Magnets are found in some commonly used medical equipment such as and Magnetic Resonance Imaging machines. MRIs use powerful magnetic fields to generate a radar-like radio signal from inside the body, using the signal to create a clear, detailed picture of bones, organs and other tissue. An MRI magnet is very strong – thousands of times more powerful than common kitchen magnets. Another medical use for magnets is for treating cancer. A doctor injects a magnetically-sensitive fluid into the cancer area and uses a powerful magnet to generate heat in the body. The heat kills the cancer cells without harming healthy organs.

In the Home

Though it may not be obvious, most homes contain many magnets. Refrigerator magnets hold papers, bottle openers and other small items to the metal refrigerator door. A pocket compass uses a magnetic needle to show which way is north. The dark magnetic strip on the backside of a credit card stores data in much the same way as a computer’s hard drive does. Vacuum cleaners, blenders and washing machines all have electric motors that work by magnetic principles. You’ll find magnets in phones, door bells, shower curtain weights and children's toys.
kavan yeo[15]

 Goh Ray Chard (12)

A permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field. An everyday example is a refrigerator magnet used to hold notes on a refrigerator door. Materials that can be magnetized, which are also the ones that are strongly attracted to a magnet, are called ferromagnetic (or ferrimagnetic). These include iron, nickel, cobalt, some alloys of rare-earth metals, and some naturally occurring minerals such as lodestone. Although ferromagnetic (and ferrimagnetic) materials are the only ones attracted to a magnet strongly enough to be commonly considered magnetic, all other substances respond weakly to a magnetic field, by one of several other types of magnetism.


Bryan Lee (19)

The key element of the toy is the magnetophoretic display panel, filled with a thick, opaque white liquid containing tiny dark magnetic particles. These particles can be drawn to the drawing surface by a magnet-tipped stylus or optionally-provided shapes, or removed to the hidden back side by a sliding eraser bar. The middle layer is divided into a honeycomb of cells, keeping the liquid static and the particles evenly distributed across the panel. The liquid is formulated so that the floating particles can be pulled through it in response to the magnetic forces, but not due to gravity.^[1]

The toy was originally produced as "Magna Doodle" by Tyco until 1997, when Tyco was purchased by Mattel. Mattel then sold the toy under its Fisher-Price brand. The brand was later sold to the Ohio Art Company. Today, the "Magna Doodle" brand is owned by Cra-Z-Art. Fisher-Price have produced their own alternative called the Doodle Pro, while Ohio Art produced the similar Doodle Sketch until 2016 when it sold the brand to Spin Master. The Doodle Pro is still available in the UK from the distribution company Megatel LTD.

Because the Magna Doodle uses no ink or graphite, scuba instructors use it as an underwater whiteboard when instructing students, and divers who wish to pass short notes.^{[citation needed]} The Magna Doodle is not specifically designed to work underwater and many of its components can rust or otherwise deteriorate over time.
Bryan lee (19

Permanent Magnet

The telephone's speaker contains a permanent magnet--one that retains its magnetism constantly. The "north" on this magnet points toward the speaker membrane.

Electromagnet

The wire coil that carries electrical current to the speaker works as an electromagnet, becoming charged with magnetism only when current travels through it.

Interaction

As the electrical current travels through the wire, the wire magnetizes and demagnetizes many times per second, interacting with the permanent magnet to push and pull the speaker membrane into vibration.

Frequency Reproduction

To reproduce natural sound frequencies, the speaker membrane must vibrate at a certain number of cycles per second, requiring the magnetic field to change direction at the same frequency. The pitch "A," for instance, requires 440 magnetic-field reversals per second.

Ashleigh

But powerful electromagnets in the tube's neck deflect the electrons toward the top or bottom and left or right sides of the tube. The inside of the screen has a special coating that glows when the stream of electrons strikes it. In this way, magnets help us see images on the TV screen.


Lucas Ritchie (25)