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Magnetism

Magnetism. Simple if you accept the rules, complex if you must know why ?. What are Magnets?.

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Magnetism

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  1. Magnetism Simple if you accept the rules, complex if you must know why?

  2. What are Magnets? • A magnet is any object that has a magnetic field. It attracts ferrous objects like pieces of iron, steel, nickel and cobalt. Since those elements are easily “magnetized” they can act as magnets themselves. Though magnets can be made of these metals, most magnets today are synthetic.

  3. Types of Magnets • One of the most common magnets - the bar magnet - is a long, rectangular bar that attracts pieces of ferrous objects. • The compass needle is a tiny magnet which is free to move horizontally on a pivot. One end of the compass needle points in the North direction and the other end points in the South direction. The end of a freely pivoted magnet will always point in the North-South direction. Why? Earth is a magnet due to its iron core. • The end that points North is called the North Pole of the magnet and the end that points South is called the South Pole of the magnet. It has been proven by experiments that like magnetic poles repel each other whereas unlike poles attract each other.

  4. What is a Magnetic Field? • The space surrounding a magnet, in which magnetic force is exerted. • As described by drawing the magnetic lines of force, when a small north magnetic pole (such as an iron filing) is placed in the magnetic field created by a magnet, it will experience a force. And if it is free to move, then it will move under the influence of magnetic field. • The path traced by a North magnetic pole free to move under the influence of a magnetic field is called a magnetic line of force. In other words, the magnetic lines of force are the lines drawn in a magnetic field along which a small North magnetic pole would move.

  5. How is a magnetic field created? When electrical current flows in a wire, a magnetic field is created around the wire. From this it has been inferred that magnetic fields are produced by the motion of electrical charges. A magnetic field of a bar magnet thus results from the motion of negatively charged electrons in or around the magnet.

  6. But do the electrons really jump from atom to atom in a magnet to create the magnetic field? No, and this is where the idea get’s complicated… • To put it as simply as possible, it has to do with the number and arrangement of valence electrons. In the diagrams below, notice that iron and nickel (ferrous elements) each have two lonely electrons in their outer shell, whereas the inner shells are full with even numbers of electrons…

  7. Notice how there are always an even number of electrons in the full, inner shells. Each one of these electrons spins in the opposite direction of another, thus, each moving electron cancels the electrical current/magnetic field of the other. • For some reason, the lonely electrons in the out shell spin in the same direction, thus, each atom generates it’s own tiny electrical current/magnetic field.

  8. Magnetic Not Magnetic • This naturally causes the south pole of each atom to point toward the north pole of another atom. • Now, with all of the valence electrons from every atom spinning in a uniform direction, they generate an overall electrical current which results in a magnetic field! • This appears to be a defining property of ferrous substances. North South

  9. How to make a natural compass: • http://www.youtube.com/watch?v=0HqW5m9yzgM • Here’s what VSauce has to say about Magnets: • http://www.youtube.com/watch?v=NSYQ2-rbREI

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