1. Chapter 19 - Magnetism and Electromagnetism

2. Over 2,000 years ago - an area of Greece known as Magnesia was noted for unusual rocks The rock, allowed to swing on a string always pointed the same way - towards the north star (leading star or load star) Magnetic rock (loadstone) contains iron

3. N – north seeking pole S – south seeking pole Like poles repel Opposite poles attract

4. Magnetic fields are created by a moving charge. The spinning of an electron (like a top) creates a tiny magnetic field. Most electrons are paired into orbitals and spin in opposite directions so their magnetic fields attract. When two opposite magnetic fields combine they cancel each other out.

5. Requirements for something to be magnetic –It must have unpaired electrons –The unpaired electrons must spin in the same direction so the magnetic fields add. –Iron, nickel and cobalt all have unpaired electrons and can be magnetized.

6. Magnetic domain – a region where the unpaired electrons spin the same direction so their magnetic fields add. In a magnetized material the domains are arranged in the same direction. see photo of magnetic domain walls see photo of magnetic domain walls

7. Iron materials can be temporary magnets by an imposed magnetic field. In picking up paperclips with a magnet, the paperclips become a temporary magnet.

8. The Earth is a giant magnet It contains molten iron and nickel at the core. (not fully understood) Geographic north – the point around which the earth rotates. (Is the north of maps) Magnetic north – the point on the earth that the compass points to. Magnetic declination – the difference in degrees between true north and magnetic north It is very little (about zero) in this area

9. Van Allen Belts – two doughnut shaped regions far above the earth (1,000 to 25,000 km) that contain high speed protons and electrons

10. Solar wind – a stream of electrically charged particles that comes from the sun. Magnetosphere – the earth’s magnetic field as shaped by the solar wind.

11. Northern lights – caused by charged particles from space entering the earth’s magnetic field (magnetosphere)

12. The earth makes magnets Molten rock that contains iron becomes magnetized by the earth as it hardens. Studying ancient volcanic rock gives a history of the earth’s magnetic field. It moves over time and even reverses itself every million years or so.

13. Electric current – a movement of charged particles (such as electrons moving through a wire) A moving charge creates a magnetic field. Amp – a measure of current (electron flow per second)

14. Solenoid – a coil of wire that produces a magnetic field when electricity is run through it. http://webphysics.davidson.edu/applets/BF ield/Solenoid.html http://webphysics.davidson.edu/applets/BF ield/Solenoid.html http://www.solenoids.com/ Solenoid + iron core makes an electromagnetic