Magnetism - Magnetic Fields - Permanent MagnetsTemporary Magnets

Lodestone (also spelled loadstone) is a special type of the mineral magnetite. All varieties of magnetite display signs of magnetism, but of them, only lodestone possesses distinctly north-south polarity. Lodestone and other magnetic iron ores often occur in igneous and metamorphic rocks found around the world. Because it occurs naturally, lodestone has been known for thousands of years. Even the ancients observed that lodestone attracts iron. They pondered this mysterious behavior in their philosophical discussions and writings. The oldest known reference to lodestone’s properties appeared in 600 BC, when the Greek philosopher Thales of Miletus noted iron’s attraction to it. Thales attempted to explain the phenomenon through animism, presuming that the lodestone possessed a soul. The lodestone also served as the basis of primitive Chinese compasses that could roughly indicate the cardinal directions. Improved compasses eventually helped guide many great explorers to new, exciting places around the globe. Today lodestone is more commonly found in classrooms, where teachers use it to help demonstrate the basic principles of magnetism. In recent years, scientists have questioned exactly why lodestone is relatively rare compared to other kinds of magnetite. Dr. Peter Wasilewski of NASA's Goddard Space Flight Center recently demonstrated that only magnetite with a specific composition and crystal structure has the potential to become lodestone by being struck with lightning. The electric discharge that accompanies lightning creates a temporary, but very strong magnetic field. This field, Wasilewski argues, is strong enough to magnetize lodestone, while the earth’s magnetic field is not. Early Magnetism… Lodestone

Earth as a Magnet Earth's field changes over time because it is generated by the motion of molten iron alloys in the Earth's outer core (the geodynamo). The Magnetic North Pole wanders, but slowly enough that a simple compass remains useful for navigation. At random intervals (averaging several hundred thousand years) the Earth's field reverses (the north and south geomagnetic poles change places with each other). These reversals leave a record in rocks that allow Paleomagnetists to calculate past motions of continents and ocean floors as a result of plate tectonics. The region above the ionosphere, and extending several tens of thousands of kilometers into space, is called the magnetosphere. This region protects the Earth from cosmic rays that would strip away the upper atmosphere, including the ozone layer that protects the earth from harmful ultraviolet radiation.

The Sun and Earths Magnetic Fields

B-Field Strength: What is the Magnetic Field Strength/ Flux Density for each situation?

What do all of these objects have in common?

Electromagnetism (EM)- I) Moving Charges induce B-Field: Ways to Make B-Field Stronger… Ways to Make B-Field Stronger…

Electromagnetism cont… II) Moving charge feels force in B-Field: Electric Motor-

Applications of Electromagnetism

Mass Spectroscopy

Electromagnetic Induction III) Changing Flux in conductor induces Potential Difference: Electric Generator- AC (Alternating Current)

Applications of Electromagnetism