Magnetism• property of matter in which there is a

force of attraction or repulsion b/w like or unlike poles

What do we know about magnets?

• 2 Magnetically opposite poles:– North Pole and South Pole

• Like poles repel and Opposite poles attract– “We’ll get back to this later”

What types of things do magnets attract?

• “Do magnets attract all metals?”– Magnets only attract objects made of iron, cobalt,

or nickel!! • These metals are called the “Iron Triad”

– See Periodic Table

• You can also only make a magnet out of these 3 metals.

• Those “rubber” magnets have iron, cobalt or nickel in them.

1st

Magnetic Domains• The molecules of most

substances have no orientation to them.

• In a magnet, the molecules align themselves in a very specific pattern.

I wonder why?

Magnetic Field• Surrounding all magnets is a magnetic

field.• Magnetic Field is the area surrounding a

magnet where the magnetic force acts.

Magnetic Field

Lines

Magnetic Field Lines

Magnetic Field Lines always move out of the North pole and

into the South pole!!

What makes the North Pole the North Pole and the South Pole the South Pole?

It is not the N

and S stamped on them!!!!

The North Pole is the pole that the magnetic field lines move out of.The South Pole is the pole that the magnetic field lines move into.

Magnetic Field Lines• Magnetic Field lines always move out of

the North end and into the South end!!

Magnetic Field Lines of Interacting Magnets

Lines of Repulsion Lines of Attraction

Solving for Unknown Poles

Are the field lines attracting or repelling?North ____________ what?attracts

Solving for Unknown Poles

Are the field lines attracting or repelling?North __attracts______ what?

Solving for Unknown Poles

Are the field lines attracting or repelling?North ____________ what?repels

Solving for Unknown Poles

Are the field lines attracting or repelling?North __repels____ what?

Determine the unknown pole

A. North

B. South

Determine the unknown pole

A. North

B. South

Where are Magnets the strongest?

I wise man told me many years ago that

“Magnets are strongest at the poles”. That is

where the magnetic field lines are the

most concentrated.

Which of the following metals would not make a very good magnet?

A. IronB. CobaltC. AluminumD. Nickel

Mr. Garay

What happens if you break a bar magnet in half?

You get 2 bar magnets both with

a North and a South pole!!

Breaking a Bar Magnet

Where is this magnet the strongest?

A. 1 only

B. 2 only

C. 3 only

D. 1 and 3

Where is this magnet the strongest?

A. 1 only

B. 2 only

C. 3 only

D. 1 and 2

If you broke a bar magnet in half and then broke both halves in half again, how many bar magnets would you have?

A. Not possibleB. 2C. 4D. 8

Note-taking Skills Worksheet

• A. Magnetism—the properties and interactions of magnets.– 1.Interaction b/w 2 magnets, called

magnetic force, increases as magnets move closer together.

– 2. A magnetic field, which exerts the magnetic force, surrounds a magnet, and is closest to the magnet.

Note-taking(cont.)

• B. Magnetic Poles—the region of a magnet where the magnetic force exerted by the magnet is strongest.– 1. All magnets have a north and a south pole.– 2. Like poles repel. Unlike poles attract.– 3. Earth has magnetic poles.

• A) A compass needle is a small bar magnet that can freely rotate.

• B) A compass needle always points north.

Note-taking(cont.)

• C. Magnetic materials—iron, cobalt, and nickel– 1. The magnetic field created by each atom exerts

a force on nearby atoms.– 2. Magnetic domains—groups of atoms with

aligned magnetic poles.• A) In a magnet, the like poles of all the domains point in

the same direction.• B) Permanent magnets are made by placing a magnetic

material in a strong magnetic field, forcing a large number of magnetic domains to line up.

Any

Questi

ons?

?