21.1 Magnets and Magnetic Fields

The green magnet and lower red magnet _________ each other.

The lower red magnet and the yellow magnet _________each other.

attract

repel

21.1 Magnets and Magnetic Fields

How do magnetic poles interact?

Magnetic Forces

How can a magnetic field affect a magnet that enters the field?

Why are some materials magnetic while others are not?

21.1 Magnets and Magnetic Fields

Magnetic force is the force a magnet exerts on another _________, on iron or a similar metal, or on moving ___________.

• Magnetic forces, like electric forces, varies with ______________.

• When you push down on the top two magnets, you feel the magnets _______________. If you push harder, the ___________ increases.

Magnetic Forces

magnet

charges

distance

repelforce

21.1 Magnets and Magnetic Fields

All magnets have two magnetic poles, regions where the magnet’s force is _______________.

• One end of a magnet is its ________ pole and the other end is its ___________ pole.

Magnetic Forces

strongest

northsouth

21.1 Magnets and Magnetic Fields

A magnetic field surrounds a magnet and can exert magnetic forces. Magnetic field lines begin near the _______ pole and extend toward the _______ pole.

• Where lines are close together, the field is __________.

• Where lines are more spread out, the field is __________.

Magnetic Fields

north

south

strong

weak

21.1 Magnets and Magnetic Fields

Magnetic Fields Around Magnets

You can use ________ filings to visualize how magnetic fields of two magnets interact.

The strength of the magnetic field in a particular area is indicated by the __________ of iron filings.

Magnetic Fields

iron

density

21.1 Magnets and Magnetic Fields

When like poles of two magnets come together, the magnets __________ each other.

Magnetic Fields

repel

21.1 Magnets and Magnetic Fields

Magnetic Fields

When opposite poles of magnets come together, the magnets ___________ each other.

attract

21.1 Magnets and Magnetic Fields

Magnetic Field Around Earth

Earth is like a giant ________ surrounded by a magnetic field. The area surrounding Earth that is influenced by this field is the ________________.

A compass points north because it aligns with Earth’s ___________ field.

Magnetic Fields

magnetosphere

magnetic

magnet

21.1 Magnets and Magnetic Fields

Earth is surrounded by magnetic field lines. These lines are _________at the poles.

Magnetic Fields

Geographic North Pole Magnetic North Pole

Geographic South Pole

Magnetic South Pole

Magnetic Field

densest

21.1 Magnets and Magnetic Fields

A property of electrons called _________ causes electrons to act like tiny magnets.

• In many materials, each __________ is paired with another having an opposite spin so magnetic effects mostly __________ each other.

Magnetic Materials

“spin”

electron

cancel

21.1 Magnets and Magnetic Fields

In a few materials, such as iron, nickel, and cobalt, the __________ electrons make a strong magnetic field.

• The fields combine to form ____________ ____________which is a region that has very large number of atoms with aligned magnetic fields.

Magnetic Materials

unpaired

magneticdomains

21.1 Magnets and Magnetic Fields

Magnetic MaterialsA ferromagnetic material, such as iron, is a material that can be _______________ because it contains magnetic domains.

• If a material is ferromagnetic, it is not always a __________; the domains do have to be aligned with each other.

magnetized

magnet

Before magnetism After magnetism

21.1 Magnets and Magnetic Fields

Magnetized Materials• Magnetization can be ____________. If the material is

moved away from the magnet, the magnetic domains become _________ again.

• In some ferromagnetic materials, the domains stay aligned for a long time. These materials are called ____________ magnets.

Magnetic Materials

temporary

random

permanent

21.1 Magnets and Magnetic Fields

If you cut a magnet in half, each half will have its own ________ pole and _______ pole because the domains will still be aligned.

A magnet can never have just a _______ pole or just a ________ pole.

Magnetic Materials

north south

north

south

21.1 Magnets and Magnetic Fields

Assessment Questions

1. Where does the magnetic field of a magnet have the strongest effect on another magnet? a. the north pole

b. the south pole

c. both poles equally

d. midway between the two poles

21.1 Magnets and Magnetic Fields

Assessment Questions

2. What happens to two magnets if they are lined up with their north poles near one another?

a. The magnets are attracted to each other.b. The magnets repel each other.c. The magnets attract each other sometimes and repel each other

the other times.d. The magnets do nothing.

21.1 Magnets and Magnetic Fields

Assessment Questions

3. What happens to an iron nail if it’s moved away from a permanent magnet?

a. The magnetic field reverses direction.

b. The magnetic domains become random again.

c. It has several north poles and several south poles.

d. It cannot be magnetized again.