Chapter 19 Section 2 & 3 Magnetic Domains and the Earth

1. Chapter 19 Section 2 & 3Magnetic Domains and the Earth GFutch CMS

2. Magnetic Domains • Matter is made of atoms. • Nucleus = center= protons (positive charge) & neutrons (neutral) • Electrons = outside nucleus= negative charge • Spinning electrons produce a magnetic field that acts like a tiny magnet.

3. Most atoms have electron pairs that spin in opposite directions and cancel out the magnetic field. • Therefore most matter have weak magnetic properties. • When electrons are NOT paired the matter have strong magnetic properties. • When magnetic fields of groups of atoms align themselves it is called a magnetic domain. • Most domains are misaligned and point in random directions.

4. Domains Magnetized Unmagnetized

5. Magnetic Materials • Materials that have domains aligned are magnetic. • Materials that show strong magnetic properties are called ferromagnetic. • Ex: • Common-nickel, cobalt, gadolinium • Rare- samarium and neodymium

7. Alloys- magnets made form several metals • Ex: • Alnico= aluminum, nickel, and cobalt • Cheap magnets are made form ferrite

8. Making & Changing Magnets • Magnets can be made, destroyed, or broken. Made • Material can be magnetized by putting it in a strong magnetic field or by rubbing it with one pole of a magnet • Temporary magnets- materials that magnetize easily but lose magnetism quickly • Permanent magnets- materials that are hard to magnetize but stay magnetized for a long time

9. Destroyed • Drop or strike a magnet hard to knock the domains out of alignment • Heating a magnet; temperature depends on material • All ferromagnetic material can lose its magnetic properties.

10. Break • If you break a magnet, the domains are still aligned. • Because the domains are still aligned, the magnet produces a strong magnetic force at the poles and a new South pole is generated.

11. Earth • Earth is a giant magnet • Has a magnetic field • Has 2 magnetic poles • Earth’s core is liquid iron & nickel • Circulation of molten material produces a magnetic field • Because Earth makes a strong magnetic field, it can make magnets out of ferromagnetic materials • The domains line up with Earth’s magnetic field.

14. A compass uses a magnetized needle that spins freely; points north • When you use a compass you must considered the magnetic declination. • The angle between the geographic pole and the magnetic pole • Angle will vary depending on your location • The magnetic declination has changed over time.

15. Earth’s Record • Earth’s magnetic field acts on magnetic material as divergent boundaries produce new rock. • Iron in molten material lines up in the direction of Earth’s magnetic field. • When the rock hardens, the iron is locked in place, leaving a record. • Scientists have studied ocean rocks and discovered that the direction and strength of Earth’s magnetic field has changed over time. • Magnetic reversals (compass points south) have happened many many times. • Why? We don’t know • Could be changes in the core

16. Magnetosphere • Earth’s magnetic field that extends into outer space that is shaped by solar winds. • Affects movements of electrically charged particles

19. Van Allen Belts- 2 inner magnetic fields that are shaped like donuts

21. Most solar wind does not penetrate the magnetic field. • When they do, they interact with the atmosphere and produce auroras (Northern Lights).