Magnetism

Magnetism – The ability of certain metals to attract iron, cobalt or nickel. The Three Types of Magnets 1) Natural 2) Artificial 3) Electromagnets The Laws of Magnetism 1) Every magnet has two poles 2) Like poles repel, unlike poles attract

The Nature of Magnetism Weber’s Theory of Magnetism (why some items can become magnetized )is based on the following observations: 1) Breaking a magnet results in each fragment becoming a whole magnet 2) Heating/hammering steel near a magnet causes it to become magnetized 3) Stroking an iron bar with a magnet causes the bar to become magnetized 4) Jarring steel filings near a magnet causes them to become magnetized.

These observations and modern day atomic theory suggest that: 1) Iron, nickel and cobalt consist of small discrete magnets 2) Magnetic materials contain magnetic domains (magnetic fields aligned in the same direction) 3) Magnetic domains consist of billions of of dipoles (magnetic poles) - In magnetized metals, the domains all line up in the same direction. - Nonmagnetized elements cannot be magnetized, because they have equal numbers of electrons spinning in each direction.

Magnetic Fields Magnets are surrounded by a magnetic field (summation of domains) or flux - The strength of a magnetic field is determined by the number of lines of flux per square cm.

Characteristics of Magnetic Lines of Force 1) They leave the north pole and enter the south pole of the magnet 2) Lines of force repel each other when traveling in the same direction & attract when going in the opposite direction

Characteristics of Magnetic Lines of Force 3) Lines of force are distorted by magnetic materials, but not non-magnetic materials.

Magnetic Induction When a magnetic material is brought near a magnet, it becomes magnetized and assumes a polarity opposite the polarity of that pole. Magnetic Induction Depends on: 1) Permeability 2) Rententivity

Magnetic Classification of Matter 1) Ferromagnetic Materials - Strong attraction to magnet 2) Paramagnetic Materials - Feeble attraction to magnet 3) Non-Magnetic - No attraction to magnet 4) Diamagnetic Materials - Repelled by magnet