What would the world be like without magnetism?

Magnets and Magnetic Fields Chapter 18 - Section 1 Pages

I. History of Magnetism Magnets are named after a place called __________ (found in present-day ________) MAGNESIA GREECE The iron-based mineral ___________ was used as a ____________ or “leading stone” almost ______ years ago. MAGNETITE LODESTONE 3,000

Lodestones were used to make primitive compasses

MAGNETISM- Background

II. Characteristics of magnets 1. Similar to the “RULE OF CHARGES”, like poles _______, unlike poles __________. 2. Always appear in _______. No matter how small the pieces of magnet are, each piece ALWAYS has ______ poles. NORTHSOUTH DIPOLE REPELATTRACT PAIRS TWO A.Have a ________ and ________ pole (called a _________)

B.Have a magnetic _______ = region where magnetic ________ may be detected FIELD FORCE POLES 1. Strongest near the ________. 2. Represented by ______________ FIELD LINES *When sprinkled around a magnet, the iron filings line up with the magnetic field *Draw a diagram in your notes (include labels!) Demonstration: Iron filings and magnets

III. What makes a magnet a magnet? A. Magnetic properties of a material depend on the motion of an atom’s ____________. The ____________ orbit the __________ of the atom and ______ like a top. ELECTRONS NUCLEUS SPIN

B. This movement of the ___ creates _____________ around each individual atom Most materials are ______ magnetic because the fields of individual atoms ________ each other out. e-e- MAGNETIC FIELDS CANCEL NOT

C.Materials that can become magnetized are called _________________. In these materials, _________________ of individual atoms are _____________________ to form a _____________________. Include ______, _________, _________ __________ form small, magnetized regions within the material FERROMAGNETIC IRON NICKEL COBALT MAGNETIC DOMAIN GROUPED TOGETHER MAGNETIC FIELDS DOMAINS

If the __________ are arranged randomly (in different ____________) the material is not a magnet. If the ___________ are aligned (in the ______ direction) the material is a _________ DOMAINS DIRECTIONS DOMAINS SAME MAGNET

Magnetic fields of the domains line up to form a larger magnetic field

DOMAINS IN ALL DIRECTIONS DOMAINS ALIGNED UNMAGNETIZED NAIL MAGNETIZED NAIL

DOMAINS

Any piece of iron can become a magnet if placed in a magnetic field. The __________ will change orientation because of the ________________ and align. DOMAINS MAGNETIC FIELD

IV. Making / destroying a magnet A.Materials that are magnetic all of the time (like ____________) are called ____________ magnets. _______________________________ __________________________________ Placing in a magnetic field (heating first is best) Stroking several times with a magnet * both ways align the ___________ of the material PERMANENT MAGNETITE FERROMAGNETIC DOMAINS B. _________________ materials may become magnets by:

C. Magnets are weakened by: __________________ _________________________________Banging…hammering..etc…the magnet Heating the magnet * ___________ are no longer aligned DOMAINS

V. The Earth as a Magnet The Earth and electrons are both magnets …sketch the Earth and its magnetic field in your notes. Magnetic South Pole Geographic North Pole

The Earth’s magnetic field protects us from solar radiation

AURORA BOREALIS AURORA AUSTRALIS

Next time: COMPASS ACTIVITY: How is a compass made? How does it work?

BIOMAGNETISM