DOWNLOAD PDF WHAT DO THE N AND THE S ON A MAGNET MEAN?

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1 Chapter 1 : Frequently Asked Questions N will attract S and S will attract N. N repels N and S repels S. It attracts all types of metals it just depends on what their polarity is. Some metals may attract to the N side and some to the S side. Are neodymium and rare earth magnets the same thing? Neodymium magnets are the most commonly used type of rare earth magnets. Rare earth magnets are made from rare earth elements found on the periodic table. Neodymium magnets are the strongest rare earth magnets and the strongest magnets in the world. Neodymium magnets are graded by the maximum strength they can be magnetized to. The higher the number the stronger the magnet is, however the higher the number the more brittle the magnet becomes as well. See Magnet Grades for more details. Can I cut, drill, or machine neodymium magnets? Machining magnets can be a tricky process and we do not recommend it unless there is no other option. Neodymium magnets are very hard and brittle and any kind of machining can break or damage the magnet. Heat produced by machining can quickly demagnetize the magnet. See After Market Machining for more details. Can I solder or weld neodymium magnets? The high heat will demagnetize the magnets and the magnets could catch fire. Do I need to worry about temperature with neodymium magnets? Neodymium magnets are sensitive to heat. Depending on the grade of the magnet, the heat will demagnetize the magnet. We can produce custom magnets that withstand high temperatures. How long does the plating last when used in salt water? Salt water is not good for NdFeB magnets as the Ni plating will corrode rapidly hrs. If a longer time is required Epoxy plating is recommended. Most of our magnets are nickel plated but we do stock some sizes in gold and epoxy plating. See Magnet Plating for more details. Do neodymium magnets lose their strength over time? Neodymium magnets are the most permanent magnets in the world. You will not even notice unless you measure it. Are there any health or safety risks with neodymium magnets? There are no known health risks caused by being exposed to neodymium magnets. There can be issues if the person has a pacemaker, so you should consult your doctor for information on this. Some people actually believe magnets can have health benefits and help the healing process. There are currently no scientific studies that prove this however. Strong magnets can cause physical harm if not handled properly, please view our Neodymium Magnet Safety page for complete details. Will magnets damage my electronics? They canâ The strong magnetic field of neodymium magnets can damage certain magnetic media such as credit cards, magnetic I. Can I damage my refrigerator, stove, oven, or microwave if I put magnets on them? No, magnets will not damage these appliances. Will magnets harm my computer or erase my hard drive? Magnets can damage magnetic tape storage media and floppy disks, so you will want to keep magnets away from these devises. The only way you could cause damage is if you place a strong neodymium magnet directly on your hard drive. Are both poles the same strength? Yes both poles are equal in strength. What is the strongest type of magnet? Neodymium magnets are the strongest magnets in the world. Can you produce monopole magnets? No, we are unable to produce monopole magnets at this time in NdFeB. Will stacking my magnets together make them stronger? Yes, when two or more magnets are stacked together they become stronger, however they will not be proportionally stronger all the time due to the nature of the material. Can you supply custom magnets? We serve the US and most international markets. You can call us or find details on our Custom Magnets Page. What is the Gauss of your magnets? The gauss varies depending on the size of magnet. All our magnets have the gauss listed in the description box of each product. Can I increase the strength of my magnet? Do you have a minimum purchase order? How do you measure the pull strength of your magnets? The pull strength of our magnets is measured by how much force it takes to pull the magnet off a steel plate when in between 2 steel plates. What kind of materials are magnets attracted to? Any kind of ferromagnetic material will attract to NdFeB magnets. Items made of Iron, Nickel or Cobalt are the most common metals that magnets are attracted to. There are also several kinds of steel that attract magnets because of its iron content. See our Ferrous Materials page for more details. Will a magnets with a 10lb pull strength lift a 10lb object? Our pull strength is tested under ideal conditions, so in real life applications you probably will not achieve the same strength. The Pull Force we measure shows how much weight it takes to pull the magnet off a piece of steel when in between 2 pieces of steel. If the application uses Page 1

2 just a magnet to metal application then the pull force is about half of what we show. Why are neodymium magnets coated? Neodymium magnets are coated to prevent oxidation and rust. Neodymium magnets are made of neodymium, iron and boron. The iron will oxidize quickly and will rust over time, the coating protects the magnet from this. Page 2

3 Chapter 2 : What does magnet mean? That's why the larger magnet is mostly the stronger magnet, even when its magnetisation classification is somewhat smaller. You can find the exact associations between these classifications and the physical values of a magnet in the table Physical magnet data. The Earth acts like a large spherical magnet: The field is generated by a dipole magnet i. This means that the north and south geographic poles and the north and south magnetic poles are not located in the same place. Often the parameters measured are the magnetic declination, D, the horizontal intensity, H, and the vertical intensity, Z. From these elements, all other parameters of the magnetic field can be calculated. Back to top What is the Main Field? These fields are superimposed on and interact with each other. This portion of the geomagnetic field is often referred to as the Main Field. The magnetosphere is shaped somewhat like a comet in response to the dynamic pressure of the solar wind. It is compressed on the side toward the sun to about 10 Earth radii and is extended tail-like on the side away from the sun to more than Earth radii. The magnetosphere deflects the flow of most solar wind particles around the Earth, while the geomagnetic field lines guide charged particle motion within the magnetosphere. Back to top What are the magnetic elements? These are declination D, inclination I, horizontal intensity H, the north X and east Y components of the horizontal intensity, vertical intensity Z, and total intensity F. The parameters describing the direction of the magnetic field are declination D and inclination I. D and I are measured in units of degrees, positive east for D and positive down for I. The intensity of the total field F is described by the horizontal component H, vertical component Z, and the north X and east Y components of the horizontal intensity. Magnetic declination is the angle between magnetic north and true north. D is considered positive when the angle measured is east of true north and negative when west. Magnetic inclination is the angle between the horizontal plane and the total field vector, measured positive into Earth. Back to top Does the magnetic field change in different locations? Yes, the magnetic field is different in different places. In fact, the magnetic field changes with both location and time. It is so irregular that it must be measured in many places to get a satisfactory picture of its distribution. This is done using satellites, and approximately operating magnetic observatories worldwide, as well as several more temporary sites. However, there are some regular features of the magnetic field. At the north magnetic pole, the north end of the dip needle is down; at the south magnetic pole, the north end is up. At the magnetic equator the dip or inclination is zero. Back to top What is a magnetic pole? The magnetic poles are defined as the area where dip I is vertical. You can also survey for the magnetic pole, using instruments that measure the magnetic field strength and direction. In practice, the geomagnetic field is not exactly vertical at these poles, but is vertical on oval-shaped loci traced on a daily basis, with considerable variation from one day to another, and approximately centered on the dip pole positions. Magnetic declination D is unreliable near the poles. More information is available at wandering poles. Back to top Where are the magnetic poles? Based on the WMM coefficients for The axis of the dipole is currently inclined at 9. The same dipole is the basis of the simple geomagnetic coordinate system. The magnetic poles or dip pole are computed from all the Gauss coefficients using an iterative method. The task of locating the principal magnetic pole by instrument is difficult for many reasons; the large area over which the dip or inclination I is nearly 90 degrees, the pole areas are not fixed points, but move tens to hundreds of kilometers because of daily variations and magnetic storms, and finally, the polar areas are relatively inaccessible to survey crews. The most recent survey determined that the Pole is moving approximately north-northwest at 55 km per year. For more details visit our page on polar wandering. Back to top What is the magnetic equator? The magnetic equator is where the dip or inclination I is zero. There is no vertical Z component to the magnetic field. The magnetic equator is not fixed, but slowly changes. North of the magnetic equator, the north end of the dip needle dips below the horizontal, I and Z are positive. South of the magnetic equator, the south end dips below the horizontal, I and Z are measured negative. As you move away from the magnetic equator, I and Z increase. This image shows the magnetic equator in green. Back to top How do I calculate the geomagnetic coordinates? There are many different definitions of geomagnetic coordinates. The simplest is to take the Page 3

4 location of the geomagnetic dipole then do a coordinate transformation from coordinates centered on the geographic pole to coordinates centered on the dipole. Longitude 0 is defined as the imaginary line from the geographic north pole to the geomagnetic north dipole. A software to calculate geomagnetic coordinates from geographic coordinates is available here. When the tectonic plates form along the oceanic ridges, the magnetic field that exists is imprinted on the rock as they cool below about Centigrade. The slowly moving plates act as a kind of tape recorder leaving information about the strength and direction of past magnetic fields. While we now appear to be in a period of declining magnetic field strength, we cannot state for certain if or when a magnetic reversal will occur. However, the present dipole moment a measure of how strong the magnetic field is is actually higher than it has been for most of the last 50, years and the current decline could reverse at any time. We expect Earth would still have a magnetic field during a reversal, but it would be weaker than normal with multiple magnetic poles. Radio communication would deteriorate, navigation by magnetic compass would be difficult and migratory animals might have problems. Back to top How often does the magnetic field reverse? During the past million years, the reversal rates vary considerably. Consecutive reversals were spaced 5 thousand years to 50 million years. The last time the magnetic field reversed was about, -, years ago. Back to top Will a reversal of the magnetic field affect animal behavior? Many migratory animals use the geomagnetic field to orient themselves. However, the mechanism underlying this ability of animals remains unknown. Experiments show that migratory birds can sense the declination and inclination of the local geomagnetic field. Changing the polarity of the horizontal magnetic field is known to affect the hanging position of bats. Some migrating butterflies use the geomagnetic field for direction. In the ocean, spiny lobsters, dolphins, and whales are known to use geomagnetic field for directions. It is thus, possible that a reversal of geomagnetic field affect the migratory behavior of some animals. Since the chance of a reversal in the near future in the next few hundred years is very low, no immediate concern is required. What are some other uses of geomagnetic measurements? Hence, magnetic exploration is a powerful tool to detect subsurface magnetic features. Magnetic surveys are typically carried out by ships or aircrafts, with magnetometers mounted on a boom - an extension from the body of the craft. Though less common, magnetic surveys are also carried out by foot. However with the use of a geomagnetic field model e. Magnetic methods are used in oil exploration to determine depth to the basement rock, in mineral exploration to detect magnetic minerals or to locate a dike dikes are tabular or sheet-like bodies of magma that cut through and across the layering of adjacent rocks, and in archaeological surveys to detect buried artifacts, grave sites etc. Magnetic surveys can also help locate ferrous objects drums, storage tanks, and in at least one well-publicized case a Cadillac car, etc. Geomagnetic Model Questions What are magnetic models and why do we need them? By constantly measuring the magnetic field, we can observe how the field is changing over a period of years. Since the field changes the way it is changing, new observations must continually be made and models generated to accurately represent the magnetic field as it is. Back to top How often are new models developed? A new one will be made available December The IGRF for Models need to be revised at least every five years because of the changing nature of the magnetic field. Existing models forward predict the magnetic field based on the rate of change in the several years preceding the model generation. Since the rate of change itself is changing, to continue to use models beyond 5 years introduces progressively greater errors in the field parameters calculated. What is the actual model range if the decimal year range is between Please note that these models are outdated and that we do not recommend its use for any purposes other than software evaluation. Write to us at geomag. For earlier than Technical reports for the older versions of WMM are available here https: The WMM is a predictive-only model and is valid for the current epoch Department of Defense, the U. The models available on our website can be split into two broad categories, predictive models designed to give magnetic field values for future dates, and historic models designed to give magnetic field values for past dates. The HDGM also includes a basic model of the external field. A,, Page 4

5 Chapter 3 : What is Faraday's law? (article) Khan Academy Fun Facts about the name Magnet. When was the first name Magnet first recorded in the United States? The oldest recorded birth by the Social Security Administration for the name Magnet is Thursday, May 16th, Jump to navigation Jump to search Bar magnet A magnet is a very special metal. When a magnet goes near a special kind of metal or other magnets, and the poles sides touching are opposite, it will pull, or attract the other metal or magnet closer. Also, if the two poles are the same, the two magnets will push away, or repel, from each other. This is called magnetism. Magnets can make some other metals into magnets when they are rubbed together. Soft magnets or impermanent magnets are often used in electromagnets. These enhance often hundreds or thousands of times the magnetic field of a wire that carries an electrical current and is wrapped around the magnet. The field of the "soft" magnet increases with the current. Permanent magnets have ferromagnetism. They occur naturally in some rocks, particularly lodestone, but are now commonly manufactured. It has to be heated at around degrees Celsius. Magnets are only attracted to special metals. Iron, cobalt and nickel are magnetic. Metals that have iron in them attract magnets well. Metals like brass, copper, zinc and aluminum are not attracted to magnets. Non-magnetic materials such as wood and glass are not attracted to magnets as they do not have magnetic materials in them. Neodymium iron boron magnets and Alnico magnets are two kinds of permanent magnet. They are a kind of rock called lodestone or magnetite. A north side of the magnet is attracted to the south side of another magnet. However, the north side of the compass points to the north pole, this can only mean that the "north pole" is really the magnetic south, and the " South magnetic pole " is really the magnetic north. The first people to discover naturally magnetic rocks were the Chinese. At first, the Chinese used the stones to carry out fortune-telling and magic tricks. Later on they used these "lodestones" to invent the compass. Page 5

6 Chapter 4 : North pole and south pole of a magnet. Physics Forums This is the magnet's Coercivity: the measure of the magnet's resistance to demagnetization by an external magnetic field. The farther left on the graph this point is located, the stronger the magnetic field you need to demagnetize the magnet. Is it possible to become addicted to playing with magnets? What is a Magnet? A magnet is an object that has a magnetic field. The word magnet comes from the Greek "magnitis lithos", which means "Magnesian stone. In the modern sense, a magnet is any material that has a magnetic field. It can be in the form of a permanent or static magnet or an electromagnet. Permanent magnets do not rely upon outside influences to generate their field. Electromagnets rely upon electric current to generate a magnetic field--when the current increases, so does the field. Back To Top What are permanent magnets made of? Modern permanent magnets are made from special alloys to create increasingly better magnets. The most common families of magnet materials today are: Neodymiums and Samarium-Cobalts are collectively known as Rare Earths. Back To Top How are magnets made? Modern magnet materials are made through casting, pressing and sintering, compression bonding, injection molding, extruding, or calendaring processes. Back To Top What does the "N rating" of the neodymium magnets mean? The grade, or "N rating" of the magnet refers to the Maximum Energy Product of the material that the magnet is made from. It refers to the maximum strength that the material can be magnetized to. Generally speaking, the higher the grade, the stronger the magnet. If a magnet is stored away from power lines, other magnets, high temperatures, and other factors that adversely affect the magnet, it will retain its magnetism essentially forever. Shock and vibration do not affect modern magnet materials, unless sufficiently strong to physically damage the material itself. The strength of a magnetic field drops off roughly exponentially over distance. Back To Top Can a magnet that has lost its magnetism be re-magnetized? Provided that the material has not been damaged by extreme heat, the magnet can be re-magnetized back to its original strength. Once a magnet is fully magnetized, it cannot be made any stronger - it is "saturated". In that sense, magnets are like buckets of water: Back To Top How do you measure the strength or power of a magnet? Most commonly, Gaussmeters, Magnetometers, or Pull-Testers are used to measure the strength of a magnet. Gaussmeters measure the strength in Gauss, Magnetometers measure in Gauss or arbitrary units so its easy to compare one magnet to another, and Pull-Testers can measure pull in pounds, kilograms, or other force units. Special Gaussmeters can cost several thousands of dollars. The Br value is measured under closed circuit conditions. A closed circuit magnet is not of much use. In practice, you will measure a field that is less than 13, Gauss close to the surface of the magnet. The actual measurement will depend on whether the magnet has any steel attached to it, how far away from the surface you make the measurement, and the size of the magnet assuming that the measurement is being made at room temperature. Quite often gauss magnetic strength is misquoted or exaggerated. It indicates the magnetic field strength remaining inside the magnet or at its core and represents a grade of magnetic material. This measurement is much higher than the surface gauss reading. The gauss rating is measured on the surface of the magnet and represents the magnetic flux density generated outside the magnet body. Strictly speaking this is the rating which is most useful to end users as this indicates the accessible gauss of the magnet. Surface Gauss alone does not tell you the strength of a magnet. If you have two different sized magnets with the same Surface Gauss, the larger magnet will be stronger. Or, you could have a small magnet with a high Surface Gauss that will pull less than a larger magnet with a lower Surface Gauss. Magnetic Poles are the surfaces from which the invisible lines of magnetic flux emanate and connect on return to the magnet. All magnets have two poles, a North pole and a South pole. By convention, we say that the magnetic field lines leave the North end of a magnet and enter the South end of a magnet. This is an example of a magnetic dipole "di" means two, thus two poles. If you take a bar magnet and break it into two pieces, each piece will again have a North pole and a South pole. If you take one of those pieces and break it into two, each of the smaller pieces will have a North pole and a South pole. No matter how small the pieces of the magnet become, each piece will have a North pole and a South pole. It has not been shown to be possible to end up with a single North pole or a single South pole which is a monopole "mono" means one or Page 6

7 single, thus one pole. Opposite poles attract each other North attracts South, while like poles repel North repels North, and South repels South. The Earth has a magnetic field with a North pole and a South pole. There is much confusion around this issue mainly because there are different conventions or starting points about how to define a north pole. There is an engineering and scientific convention; but there is also a medical or magnetic therapy understanding. This is why, if you hold a compass up to a magnet, the needle will point to the South pole of the magnet. Like poles repel, unlike poles attract. The magnetic therapy starting point says that the Earths geographical North Pole is a magnetic north pole, therefore whatever points to the north pole i. This is the common sense approach, i. A north pole from this point of view is often called Bio North or Negative North. The end of the compass needle with the N or arrow will point to the Bio North pole. The North pole is defined as the pole of a magnet that, when free to rotate, seeks the North pole of the Earth. In other words, the North pole of a magnet seeks the North pole of the Earth. Similarly, the South pole of a magnet seeks the South pole of the Earth. Can I buy magnets with the North Poles already marked? Yes, please see our line of pole indicated magnets. You can tell by placing a compass close to the magnet. The end of the needle that normally points toward the North pole of the Earth would point to the South pole of the magnet. What are the different types of magnets available? There are 2 types of magnets: Permanent magnets emit a magnetic field without the need for any external source of power. Electro-magnets require electricity in order to behave as a magnet. There are various different types of permanent magnet materials, each with their own unique characteristics. Each different material has a family of grades that have properties slightly different from each other, though based on the same composition. Rare Earth magnets are magnets that are made out of the Rare Earth group of elements. Back To Top Which are the strongest permanent magnets? The most powerful permanent magnets available today are the Rare Earths. However, at elevated temperatures of approximately C and above, the Samarium Cobalt types can be stronger that the Neodymium-Iron-Boron types depending on the magnetic circuit. Most modern magnet materials have a "grain" in that they can be magnetized for maximum effect only through one direction. This is the "orientation direction", also known as the "easy axis", or "axis". Unoriented magnets also known as "Isotropic magnets" are much weaker than oriented magnets, and can be magnetized in any direction. Oriented magnets also known as "Anisotropic magnets" are not the same in every direction - they have a preferred direction in which they should be magnetized. What is the pull strength of your magnets? Pull strength is a very subjective measure that is dependent upon many factors such as: Type of material being pulled against; Surface conditions; Magnet characteristics such as plating composition; and Presence or absence of lateral and rotational forces. Not easily or safely. Neodymium sintered magnets behave like a ceramic. They have a tendency to crack and chip when drilled. Additionally, the powder produced when machining these magnets is flammable. Lastly, machining causes heat to build up in the magnet which may result in it being demagnetized. Most likely, a drilled or machined Neo magnet will be made unusable by the process due to breakage, cracking or heat damage. Yes, if heated beyond degrees Fahrenheit 80 degrees Celsius the magnets will quickly loose their magnetic properties. Sustaining these temperatures for a length of time or heating the magnet significantly higher than this will permanently demagnetize it. Other types of magnets such as Samarium-Cobalt have higher heat resistance. There are also other types of Nd-Fe-B magnets that are not as susceptible to heat induced flux degradation. Back To Top Do magnets pose a health risk? No, unless you have an internal medical device such as a pacemaker that would be affected by a strong magnetic field. However, Neodymium magnets are very strong and should be handled with care. These magnets can pinch if allowed to come together against the skin and larger magnets are capable of breaking bones. For this reason, children should not be allowed to play with the larger magnets. Back To Top Can magnets cure disease? Page 7

8 Chapter 5 : Neodymium Super Magnets: What does "Grade N42" mean? Freebase ( / 0 votes) Rate this definition. Magnet. A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, and attracts or repels other magnets. Here are all the possible meanings and translations of the word magnet. Magnet noun the loadstone; a species of iron ore the ferrosoferric or magnetic ore, Fe3O4 which has the property of attracting iron and some of its ores, and, when freely suspended, of pointing to the poles; -- called also natural magnet Magnet noun a bar or mass of steel or iron to which the peculiar properties of the loadstone have been imparted; -- called, in distinction from the loadstone, an artificial magnet Origin: Magnet A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: 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. These include iron, nickel, cobalt, some alloys of rare earth metals, and some naturally occurring minerals such as lodestone. Although ferromagnetic 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. Ferromagnetic materials can be divided into magnetically "soft" materials like annealed iron, which can be magnetized but do not tend to stay magnetized, and magnetically "hard" materials, which do. Permanent magnets are made from "hard" ferromagnetic materials such as alnico and ferrite that are subjected to special processing in a powerful magnetic field during manufacture, to align their internal microcrystalline structure, making them very hard to demagnetize. To demagnetize a saturated magnet, a certain magnetic field must be applied, and this threshold depends on coercivity of the respective material. Chambers 20th Century Dictionary 0. Magnet the name given to loadstone as first discovered in Magnesia, a town in Asia Minor; also to a piece of iron, nickel, or cobalt having similar properties, notably the power of setting itself in a definite direction; also a coil of wire carrying an electric current, because such a coil really possesses the properties characteristic of an iron magnet. The Standard Electrical Dictionary 0. Magnet A body which tends when suspended by its centre of gravity to lay itself in a definite direction, and to place a definite line within it, its magnetic axis, q. The same bodies have the power of attracting iron Daniell, also nickel and cobalt. Magnets are substances which possess the power of attracting iron. Edward Purcell and others have explained magnetic and electromagnetic phenomenon as relativistic effects related to electrostatic attraction. Magnetism is caused by Lorentz contraction of space along the direction of a current. Electromagnetic waves are caused by charge acceleration and the resulting disturbance of the electrostatic field. Magnets are used in a variety of instruments e. Computers, card readers, televisions, motors, generators, speakers etc. Numerology The numerical value of magnet in Chaldean Numerology is: Page 8

9 Chapter 6 : Magnet - Simple English Wikipedia, the free encyclopedia What does the "N rating" of the neodymium magnets mean? The grade, or "N rating" of the magnet refers to the Maximum Energy Product of the material that the magnet is made from. It refers to the maximum strength that the material can be magnetized to. You might also wonder about what happens between A and C and between B and D, in the positions shown. A and C repel. B and D attract. If you imagine each magnet as a tube of current going around the axis, the ones that attract are the ones where the nearby parts of the current go the same way in each tube. How do magnets stick together only sometimes? Hello Isabel- Bar magnets only sometimes stick together and sometimes repel because each has a north pole and a south pole. Opposite poles attract, and like poles repel. The picture above shows an example. In permanent magnets what sort of energy do they use to push or pull other magnets if any at all? I was also wondering does a permanent magnet ever lose its magnetism? A good permanent magnet stays that way for a very long time at room temperature. You also ask, if I understand right, what sort of energy is involved in the magnetic forces between magnets. There is energy stored in the magnetic field itself. The density of that energy is proportional to the square of the field strength. When magnets move near each other, that field energy generally changes. I know a magnet can attract steel paper clips through paper, cardboard, plastics, cloth, etc. But can a magnet attract steel paper clips through a sheet of sheet? I have beeen confused as some sources say it will not. I know you can make a iron nail a temporary magnet by attracting it to a magnet at one end and have paper clips attracted to the nail. Picture the magnetic field in the usual way, as a set of field lines coming out of one pole of the magnet and returning to the other. Some of the field lines get stuck in them. Now what happens if you put a big sheet of steel in between the magnet and the paper clips? The field lines mostly get drawn into the sheet, spread out in the sheet, and return without going past the sheet to the paperclip. This effect depends a lot on the shape of the sheet. A small piece of steel can pull field lines into it leaving more field just behind it than were there before. Each clip tends to steer field lines on to the next one. So the steel redirects the field, with a sheet redistributing it away from the clip just on the other side. It would tend to grab clips right near the edge of the sheet, where some of the field lines exit. We made electromagnets in class with wire, a large nail and a 6 volt battery. The nails were not magnetic, but after we disconnected the batteries from the nails, the nails would pick up staples. How did the battery or the electricity magnetize the nail? At room temperature the little magnets of the electrons in the iron tend to line up with other, making those magnetic domains. However, the magnetism of the different domains points all different directions, so overall it cancels out. When you put the nail in the electromagnet made with the coiled wire powered by the battery, it lines up a lot of those domains to point the same way. That means the nail is a bit magnetized. This is temporarily posted without the usual check, until Lee gets back from Paris. The answer I usually get is something like: I am aware of that. Your first question is easy. Sure, you can make a donut-shaped magnet with the N poles on the outer part and the S poles near the donut hole. Your second question is extremely hard to answer. I think for now perhaps the best non-answer is this. At that point, all you can do is describe the properties, not say what things are made of. Electromagnetic fields are pretty close to that point. We could give maybe a step or so deeper description, but it would be in terms of quantum fields. Those are even more abstract mathematical entities than magnetic fields. Well, i know that moving or spinning charged particles can cause a magnetic field. But how does it do that? And what causes those forces in the first place? For example, gravity is caused by mass curving or warping space time or something of the sort, what causes magnetic and electrostatic forces? I know very basic quantum mechanics. Look at a moving charge near a neutral, current-carrying wire. But if you now look in the rest frame of the charge, the wire is no longer neutral, thanks to the different Lorentz contractions of the differently-moving plus and minus charges. So there must have been a velocity-dependent force back in the frame where the wire was neutral. We call that velocity-dependent force magnetism. Ok, that handles the part about why magnetism, given electricity. The part about why electricity in the first place is unfortunately over my head. Purcell derives the magnetism from electricity from assuming a symmetry, special relativity, a rule about how the world obeys the same laws of Page 9

10 physics even as you represent its contents in different ways. What a neat site. These kids are so smart! Also, to Atticus and the other brilliant kids who ask the right questions, give them more questions that they can access and imagine! One that I have often pondered please answer: What do you see when looking through an infinitely powerful microscope? What is a particle made of the smallest one? Then the question is of course what is energy? Is there an answer to this question? Or is it unanswerable? We were just discussing doing more to encourage our readers to do experiments. Your suggestion about raising follow-up questions for them is along the same lines. We think of the magnetic field as a real thing, all spread out in space, acting where it is. But how did that field get all spread-out? Not by sudden action-at-a-distance. It had to work its way over from the source, by an electromagnetic wave traveling at the speed of light. Right now, the deepest things we know are all differential equations, but some people suspect that may change. Adding bar magnets together Q: If you place two equally strong magnets together so they attract do the act as a single magnet with one magnetic field? Will the resulting magnet be twice as strong as one of the original magnets? Hi Mark, If you have two thin bar magnets and put them together in parallel the resulting strength is about double. If you keep adding more and more of them eventually the resulting sum is not the sum of the number of magnets due to the over all geometry of the combination. It involves some integrals. Does positive attract positive? People say Positive energy attracts Positive. But how is this possible if they repel each other? Or is that a bunch of bull? My mom bought 2 expensive bar magnets to stand on while exercising. Is she nuts or is this true? This old physics has nothing to do with various new-age ideas. Magnets are still another matter. No magnetic charges "monopoles" have ever been found. Your mom may not be nuts because many medical conditions are known to be helped by something called the placebo effect. People who believe that something e. Magnets are truly harmless. I have a lot of trouble motivating myself to exercise enough. Storing energy in magnets Q: Is there a way to create energy from magnets? For example, when putting the same end of a magnet together, the magnets push away from each other. Where does this energy come from? Would it be possible to create giant magnets or contained magnetic fields in order to create energy and power mechanisms? Understanding that all energy is simply transferred but not newly created, where is this energy coming from? Page 10

11 Chapter 7 : Geomagnetism Frequently Asked Questions NCEI As a very general rule, the higher the grade (the number following the 'N'), the stronger the magnet. The highest grade of neodymium magnet currently available is N Any letter following the grade refers to the temperature rating of the magnet. Magnetic field The magnetic flux density also called magnetic B field or just magnetic field, usually denoted B is a vector field. The magnetic B field vector at a given point in space is specified by two properties: Its direction, which is along the orientation of a compass needle. Its magnitude also called strength, which is proportional to how strongly the compass needle orients along that direction. In SI units, the strength of the magnetic B field is given in teslas. A magnet both produces its own magnetic field and responds to magnetic fields. The strength of the magnetic field it produces is at any given point proportional to the magnitude of its magnetic moment. In addition, when the magnet is put into an external magnetic field, produced by a different source, it is subject to a torque tending to orient the magnetic moment parallel to the field. A magnet may also be subject to a force driving it in one direction or another, according to the positions and orientations of the magnet and source. If the field is uniform in space, the magnet is subject to no net force, although it is subject to a torque. A good bar magnet may have a magnetic moment of magnitude 0. Iron can have a magnetization of around a million amperes per meter. Such a large value explains why iron magnets are so effective at producing magnetic fields. Modelling magnets See also: Two definitions of moment Two different models exist for magnets: Although for many purposes it is convenient to think of a magnet as having distinct north and south magnetic poles, the concept of poles should not be taken literally: The magnet does not have distinct north or south particles on opposing sides. If a bar magnet is broken into two pieces, in an attempt to separate the north and south poles, the result will be two bar magnets, each of which has both a north and south pole. However, a version of the magnetic-pole approach is used by professional magneticians to design permanent magnets. This is a mathematical convenience and does not imply that there are actually monopoles in the magnet. If the magnetic-pole distribution is known, then the pole model gives the magnetic field H. Outside the magnet, the field B is proportional to H, while inside the magnetization must be added to H. An extension of this method that allows for internal magnetic charges is used in theories of ferromagnetism. For a uniformly magnetized cylindrical bar magnet, the net effect of the microscopic bound currents is to make the magnet behave as if there is a macroscopic sheet of electric current flowing around the surface, with local flow direction normal to the cylinder axis. For example, one method would be to compare it to an electromagnet, whose poles can be identified by the right-hand rule. Magnetism The term magnet is typically reserved for objects that produce their own persistent magnetic field even in the absence of an applied magnetic field. Only certain classes of materials can do this. Most materials, however, produce a magnetic field in response to an applied magnetic field â a phenomenon known as magnetism. There are several types of magnetism, and all materials exhibit at least one of them. The overall magnetic behavior of a material can vary widely, depending on the structure of the material, particularly on its electron configuration. Several forms of magnetic behavior have been observed in different materials, including: Ferromagnetic and ferrimagnetic materials are the ones normally thought of as magnetic; they are attracted to a magnet strongly enough that the attraction can be felt. These materials are the only ones that can retain magnetization and become magnets; a common example is a traditional refrigerator magnet. Ferrimagnetic materials, which include ferrites and the oldest magnetic materials magnetite and lodestone, are similar to but weaker than ferromagnetics. The difference between ferro- and ferrimagnetic materials is related to their microscopic structure, as explained in Magnetism. Paramagnetic substances, such as platinum, aluminum, and oxygen, are weakly attracted to either pole of a magnet. This attraction is hundreds of thousands of times weaker than that of ferromagnetic materials, so it can only be detected by using sensitive instruments or using extremely strong magnets. Magnetic ferrofluids, although they are made of tiny ferromagnetic particles suspended in liquid, are sometimes considered paramagnetic since they cannot be magnetized. Diamagnetic means repelled by both poles. Compared to paramagnetic and ferromagnetic substances, diamagnetic substances, such as carbon, copper, water, and Page 11

12 plastic, are even more weakly repelled by a magnet. The permeability of diamagnetic materials is less than the permeability of a vacuum. All substances not possessing one of the other types of magnetism are diamagnetic; this includes most substances. Although force on a diamagnetic object from an ordinary magnet is far too weak to be felt, using extremely strong superconducting magnets, diamagnetic objects such as pieces of lead and even mice [19] can be levitated, so they float in mid-air. Superconductors repel magnetic fields from their interior and are strongly diamagnetic. There are various other types of magnetism, such as spin glass, superparamagnetism, superdiamagnetism, and metamagnetism. Common uses Hard disk drives record data on a thin magnetic coating Magnetic hand separator for heavy minerals Magnetic recording media: VHS tapes contain a reel of magnetic tape. The information that makes up the video and sound is encoded on the magnetic coating on the tape. Common audio cassettes also rely on magnetic tape. Similarly, in computers, floppy disks and hard disks record data on a thin magnetic coating. All of these cards have a magnetic strip on one side. TV and computer screens containing a cathode ray tube employ an electromagnet to guide electrons to the screen. Most speakers employ a permanent magnet and a current-carrying coil to convert electric energy the signal into mechanical energy movement that creates the sound. The coil is wrapped around a bobbin attached to the speaker cone and carries the signal as changing current that interacts with the field of the permanent magnet. The voice coil feels a magnetic force and in response, moves the cone and pressurizes the neighboring air, thus generating sound. Dynamic microphones employ the same concept, but in reverse. A microphone has a diaphragm or membrane attached to a coil of wire. The coil rests inside a specially shaped magnet. When sound vibrates the membrane, the coil is vibrated as well. As the coil moves through the magnetic field, a voltage is induced across the coil. This voltage drives a current in the wire that is characteristic of the original sound. Electric guitars use magnetic pickups to transduce the vibration of guitar strings into electric current that can then be amplified. This is different from the principle behind the speaker and dynamic microphone because the vibrations are sensed directly by the magnet, and a diaphragm is not employed. The Hammond organ used a similar principle, with rotating tonewheels instead of strings. Electric motors and generators: Some electric motors rely upon a combination of an electromagnet and a permanent magnet, and, much like loudspeakers, they convert electric energy into mechanical energy. A generator is the reverse: Chemists use nuclear magnetic resonance to characterize synthesized compounds. Chucks are used in the metalworking field to hold objects. Magnets are also used in other types of fastening devices, such as the magnetic base, the magnetic clamp and the refrigerator magnet. Vinyl magnet sheets may be attached to paintings, photographs, and other ornamental articles, allowing them to be attached to refrigerators and other metal surfaces. Objects and paint can be applied directly to the magnet surface to create collage pieces of art. Magnetic art is portable, inexpensive and easy to create. Vinyl magnetic art is not for the refrigerator anymore. Colorful metal magnetic boards, strips, doors, microwave ovens, dishwashers, cars, metal I beams, and any metal surface can be receptive of magnetic vinyl art. Being a relatively new media for art, the creative uses for this material is just beginning. Many topic questions are based on magnets, including the repulsion of current-carrying wires, the effect of temperature, and motors involving magnets. M-tic uses magnetic rods connected to metal spheres for construction. Note the geodesic tetrahedron Toys: Refrigerator magnets are used to adorn kitchens, as a souvenir, or simply to hold a note or photo to the refrigerator door. Magnets can be used to make jewelry. Necklaces and bracelets can have a magnetic clasp, or may be constructed entirely from a linked series of magnets and ferrous beads. Magnets can pick up magnetic items iron nails, staples, tacks, paper clips that are either too small, too hard to reach, or too thin for fingers to hold. Some screwdrivers are magnetized for this purpose. Magnets can be used in scrap and salvage operations to separate magnetic metals iron, cobalt, and nickel from non-magnetic metals aluminum, non-ferrous alloys, etc. The same idea can be used in the so-called "magnet test", in which an auto body is inspected with a magnet to detect areas repaired using fiberglass or plastic putty. Magnets are found in process industries, food manufacturing especially, in order to remove metal foreign bodies from materials entering the process raw materials or to detect a possible contamination at the end of the process and prior to packaging. They constitute an important layer of protection for the process equipment and for the final consumer. Eliminating rolling resistance increases efficiency. Magnets may be used to serve as a fail-safe device for some cable connections. For Page 12

13 example, the power cords of some laptops are magnetic to prevent accidental damage to the port when tripped over. Medical issues and safety Because human tissues have a very low level of susceptibility to static magnetic fields, there is little mainstream scientific evidence showing a health effect associated with exposure to static fields. Dynamic magnetic fields may be a different issue, however; correlations between electromagnetic radiation and cancer rates have been postulated due to demographic correlations see Electromagnetic radiation and health. If a ferromagnetic foreign body is present in human tissue, an external magnetic field interacting with it can pose a serious safety risk. It is for this reason that a patient with the device installed cannot be tested with the use of a magnetic resonance imaging device. Children sometimes swallow small magnets from toys, and this can be hazardous if two or more magnets are swallowed, as the magnets can pinch or puncture internal tissues; one death has been reported. MRIs generate enormous magnetic fields, and therefore rooms intended to hold them exclude ferrous metals. Bringing objects made of ferrous metals such as oxygen canisters into such a room creates a severe safety risk, as those objects may be powerfully thrown about by the intense magnetic fields. Magnetizing ferromagnets See also: Chapter 8 : what does 14,gs in a magnet mean? Yahoo Answers The strong magnetic field of neodymium magnets can damage certain magnetic media such as credit cards, magnetic I.D. cards, cassette tapes and video tapes. They can also cause damage to TV's, computer monitors and other CRT displays. Chapter 9 : What do S and N on a magnet mean? Yahoo Answers Having the properties of a magnet; i.e. of attracting iron or steel ("the hard disk is covered with a thin coat of magnetic material") Synonyms: magnetised and magnetized Determined by earth's magnetic fields (" magnetic north " and " the needle of a magnetic compass points to the magnetic north pole "). Page 13