LAUSD Keynote Presentation 6 Dec 2004
Lesson Magnetism, magnets are compasses, like poles repel, unlike poles attract, the magnetic field of the earth.
Magnetism of the planets.
Magnetism of the earth,
The geodynamo, a USGS write-up on how the earth's magnetic field is created.
California Science Standards: Topics related to magnetism grades 4 to 8.
Physical Science: Compasses, the magnetic field of the earth, magnetic poles, electromagnets.
Compasses align with the horizontal component of the earth's magnetic field. The north end of the compass points to a south pole, alas this magnetic south pole is located at the earth's geographic north pole and even more alas, on maps it is called the "north magnetic pole." The magnetic field of the earth is made by a billion amp electric current flowing in the liquid metal core of the earth.
Earth Science: Rocks types,properties, and rock cycle.; Erosion and weathering
Some igneous rocks containing iron minerals can be magnetized
Physical Science: Properties of metals
Some metals are ferromagnetic;iron nickel and cobalt, some are diamagnetic bismuth some are paramagnetic aluminum.
Solar System: Sun, star, composition, size., planets, earth and moon
The sun has a magnetic field that flips direction every 11 years creating the sunspot cycle. The sun is a rotating sphere of ionized, electrically conducting plasma. Electric currents in the sun make it an electromagnet. The core of the earth is made of iron, the earth is an electromagnet not a ferromagnetic.
Investigation: classify objects
Are objects ferromagnetic, are they diamagnetic, paramagnetic.
Plate Tectonics: Evidence for plate tectonics, results of plate motion, California Geology and plate tectonics.
Cooling lava may preserve the magnetic field at its location. The dip of the magnetic field records the latitude of formation of the rock. In addition the rock records the direction of magnetic north.
Energy in the solar system: Convection Currents, in the liquid core.
Convection currents in the liquid core of the earth shape the earth's magnetic field.
Investigation: read maps, topographic and geologic
Topographic maps show the direction of magnetic north and geographic north.
Physical Principles in Living Systems:
There are magnetic bacteria, magnetotacticum aquaspirullum that create magnetic minerals inside themselves which they use to navigate. Applying a strong magnetic field can reverse the magnetization of these bacteria which then swim to oxygen and death. Mutations that occur before death sometimes result in new bacteria with the correct magnetic orientation thus showing natural selection on a few hour timescale.
Investigation: use the world wide web for research.
Look up magnetotacticum aquaspirullum, look up the magnetic fields of the planets and the sun, look up the solar cycle.
Forces have direction and magnitude.
Magnetic forces can be attractive or repulsive. The magnitude of the force decreases with distance. The force between to dipole magnets decreases as 1/r^4 at large distances (not as 1/r^2 as mentioned in many texts.)
Earth in the Solar System: solar system composition, magnetic fields of the planets.
The Earth, Jupiter,Saturn, Uranus and Neptune's are planets with sizable magnetic fields.
Periodic Table: atomic number, classification by properties.
Every element has diamagnetic properties, e.g. He. Many have stronger paramagnetism which swamps the diamagnetism. e.g. H A few have strong ferromagnetism, e.g. Fe.