What would the world be like without

magnetism?

Magnets and Magnetic Fields

Chapter 18 - Section 1

Pages 619-625

I. History of Magnetism• Magnets are named after a place called __________ (found in present-day ________)

MAGNESIA

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.

NORTH SOUTHDIPOLE

REPEL ATTRACT

PAIRS

TWO

A. Have a ________ and ________ pole (called a _________)

B. Have a magnetic _______ = region where magnetic ________ may be detected

FIELDFORCE

POLES1. 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.

ELECTRONSELECTRONS NUCLEUS

SPIN

B. This movement of the ___ creates _____________ around each individual atom

• Electrons are in pairs. Electrons spin (in opposite directions up/down) and magnetic fields cancel each other not magnetic

• When electrons ______________, magnetic fields ________________ creating a magnetic material!

e-

MAGNETIC FIELDS

DO NOT HAVE A PAIR

DON’T CANCEL OUT

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 DOMAINGROUPED 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

SAMEMAGNET

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

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

PERMANENTMAGNETITE

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

SUN SPOTS!

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

work?

BIOMAGNETISM