Slide 1 : Magnetism
Slide 2 : Magnets have been known for centuries.
The Chinese and Greeks knew about the “magical” properties of magnets. The ancient Greeks used a stone substance called “magnetite.” They discovered that the stone always pointed in the same direction. Later, stones of magnetite called “lodestones” were used in navigation.
Slide 3 : William Gilbert, an English physician, first proposed in 1600 that the earth itself is a magnet, and he predicted that the Earth would be found to have magnetic poles.
Slide 4 : What is Magnetism? Magnetism is the force of attraction or repulsion of a magnetic material due to the arrangement of its atoms, particularly its electrons.
Slide 5 : The ends of a magnet are where the magnetic effect is the
strongest. These are called “poles.” Each magnet has
2 poles – 1 north, 1 south.
Slide 6 : Like repels like… Opposites attract!
Slide 7 : Poles of a magnet always
Come in pairs!
Slide 8 : If you cut a magnet in half, you get 2 magnets!
Slide 9 : Magnetic Fields The region where the magnetic forces
act is called the “magnetic field”
Slide 10 : Atoms themselves have magnetic properties due
to the spin of the atom’s electrons. These areas of atoms are called “domains” Groups of atoms join so that their magnetic fields
are all going in the same direction
Slide 11 : When an unmagnetized substance is placed in a magnetic
field, the substance can become magnetized.
This happens when the spinning electrons line up in the
same direction.
Slide 12 : An unmagnetized substance looks like
this…
Slide 13 : While a magnetized substance looks
like this…
Slide 14 : How to break a magnet: 1. Drop it 2. Heat it This causes the domains to become random again!
Slide 15 : The Earth is a magnet: Magnetic South Pole Magnetic North Pole It exerts magnetic forces and is surrounded by a
magnetic field that is strongest near the
North and South
magnetic poles Geographic North Pole Geographic South Pole
Slide 16 : Sometimes, the Earth’s magnetic poles flip. This happens every half-million years or so. Magnetic North Pole Magnetic South Pole
Slide 17 : We use the Earth’s magnetic field to find direction. The needle of a compass always points toward the magnetic south pole. We call this direction “North” (remember, opposites attract)
Slide 18 : The sun has a magnetic field, too. It extends far above the sun’s surface. Other planets in the solar system also have these magnetic fields
Slide 19 : When a charged particle enters a magnetic field, an electric force is exerted on it. If a charged particle moves at an angle to a magnetic field, the magnetic force acting on it will cause it to move in a spiral around the magnetic field lines.
Slide 20 : The solar wind is constantly bombarding the Earth’s magnetic field. Sometimes these charged particles penetrate that field. These particles are found in two large regions known as the Van Allen Belts.
Slide 21 : The Earth’s magnetic field extends far into space. It is called the “magnetosphere.” When the magnetic particles from the sun, called “solar wind”, strike this magnetosphere, we see a phenomenon called…
Slide 22 : The Aurora Borealis in the Northern Hemisphere And the Aurora Australis in the Southern Hemisphere
Slide 23 :