FERROMAGNETIC PARAMAGNETIC DIAMAGNETIC Materials may be classified as: FERROMAGNETIC strongly attracted to magnets iron, steel, cobalt, nickel PARAMAGNETIC slightly attracted by strong magnets wood, aluminum, platinum, oxygen DIAMAGNETIC slightly repelled by strong magnets zinc, bismuth, sodium chloride, gold

Magnetism is a property of charge in motion. Orbiting electrons (negative charges in motion) in the atom produce a magnetic field. The domain theory is used to explain why some materials are, or may become, magnetic. No one knows exactly why moving charges cause magnetism.

Like poles repel; unlike poles attract. BASIC LAW OF MAGNETISM Like poles repel; unlike poles attract. Although it is possible to isolate positive and negative charges, it is impossible to isolate NORTH and SOUTH magnetic poles. Magnetic monopoles do not exist.

The north magnetic pole is not caused by protons, Even though magnetic properties are similar to electric properties, it is erroneous to directly relate positive and negative electric charges to north and south magnetic poles. The north magnetic pole is not caused by protons, nor is the south magnetic pole caused by electrons!!!!

F = G (m1m2)/d2 F = k (q1q2)/d2 F = k (M1M2)/d2 Electrostatics The force between magnetic poles follows a law similar to the Law of Universal Gravitation and Coulomb’s Law for Electrostatics. F = G (m1m2)/d2 Universal Gravitation Electrostatics F = k (q1q2)/d2 Magnetism F = k (M1M2)/d2

Click here to view some magnetic fields. Magnetic fields surround magnets. Field lines point from North to South outside the magnet. N S Click here to view some magnetic fields.

The number of field lines is known as Magnetic Flux. The unit of magnetic flux is the WEBER, named in honor of Wilhelm Weber. The amount of flux lines per unit area is known as Magnetic Flux Density. Magnetic Flux Density is measured in TESLAS, named in honor of Nikola Tesla. One Tesla is one Weber per square meter = 1 Weber/m2.

Magnetism became associated with currents when Hans Christian Oersted noticed a compass move near a wire with a current in the very early 19th century.

A magnetic field surrounds a current-bearing wire. The direction of the magnetic field can be determined by the “Right Hand Rule for a Current-Bearing Wire.” “Grasp wire with right hand so that thumb points in the direction of conventional (positive) current. Your fingers circle the wire in the direction of the magnetic field.”

Click on the following links to view computer simulated examples of how electricity and magnetism are necessarily “linked” together. magnetic field around a current-bearing wire: Link, link Lenz’s Law: Link Faraday’s Magnetic Field Induction Experiment1: Link Faraday’s Magnetic Field Induction Experiment2: Link AC Generator: Link DC Generator: Link Lorentz Force: Link magnet moving in and out of coil (movie): Link

Applications of Electromagnetic Relationships Electromagnets Electric Motors Generators