WOW !

Magnet Magic

Magnets come in all shapes and sizes.

round

flat

horseshoe

bar

rod

1/9 – Aurora Borelis1/12 – compass1/14 – magnetic field1/15 – Electromagnet1/16 – permanent

magnet.

1/9 – explain how the Earth’s magnetic field protects us.

1/12 – Explain how the earth’s magnetic field protects us.

1/14 – Draw a magnetic field around a magnet.

1/15 – Describe how you might create an electromagnet.

1/16 – Describe how to decrease the force of an electromagnet.

Explain how animals use the Earth’s magnetic field.

Explain why a compass points North. Describe how to create an electromagnetic. Explain how to increase or decrease the

strength of a magnet. Explain what made the nail a magnet. Explain how to create a magnet. Name the type of material magnets are made.

4

Name the 3 types of magnets. Draw a magnetic field. Describe what creates the Earth’s magnetic field. Describe how the Earth’s magnetic field protects

the Earth. Contrast permanent magnets and

electromagnets. Describe what creates the Aurora Borelais. Explain how to create a compass. Explain why a compass always points North.

5

Magnets have been known for centuries.Magnets have been known for centuries.The Chinese and Greeks knew about the The Chinese and Greeks knew about the ““magicalmagical”” properties of magnets. The properties of magnets. The ancient Greeks used a stone substance ancient Greeks used a stone substance called called ““magnetite.magnetite.”” It was discovered near It was discovered near Magnesta so called it magnetite.They Magnesta so called it magnetite.They discovered that the stone always pointed in discovered that the stone always pointed in the same direction. Later, stones of the same direction. Later, stones of magnetite called magnetite called ““lodestoneslodestones”” were used in were used in navigation.navigation.

What is Magnetism?What is Magnetism?

Magnetism is the force of attraction or repulsion of a magnetic material due to the arrangement of its atoms, particularly its electrons.

Magnet Any material that attracts iron or materials

containing iron caused by alignment of electrons.

9

Magnetic Attraction

Magnets attract metals such as iron, nickel, and cobalt

3 Properties of Magnets

1. 2 poles

2. Exert forces

3. Surrounded by magnetic field

11

12

A magnet – strongest part is at the poles!!!

has anorth poleand a south

pole.

S N

What Increases Strengthen of Magnet?

The strength of the force between magnets depends on the distance between them.

The magnetic force decreases with distance much faster than does either gravity or the electric force.

What Creates Magnetic Material?

14

What Makes Materials Magnetic? Moving electrons produce magnetic fields

that gives an atom a north or south pole. In certain materials, the atoms line up to

create magnetic fields which create domains.

You can create a magnet by rubbing an iron nail with a magnet.

15

Magnetic Properties of Materials

Magnetic domains in a ferromagnetic material will always orient themselves to attract a permanent magnet. If a north pole approaches, domains grow that have south poles

facing out. If a south pole approaches, domains grow that have north poles

facing out.

Properties of Magnets

Key Question:

How do magnets interact with each other?

19

The north pole attracts the south pole of the other magnet.

S N S N

S N S N

20

The north pole repels the north pole of the other magnet.

You can feel the magnets pushing apart.

This is called repulsion

Note - south poles also repel each other

S N S N

Like repels like…Like repels like…

Opposites attract!Opposites attract!

Magnetic Fields

The field around a magnet where the magnetic forces can act.

Lines can be drawn to show the magnetic field around a magnet.

22

Magnetic FieldsMagnetic Fields

The region where the magnetic forcesThe region where the magnetic forcesact is called the act is called the ““magnetic fieldmagnetic field””

The magnetic field The number of field lines in a

certain area indicates the relative strength of the magnetic field in that area.

The arrows on the field lines indicate the direction of the force.

The closer the lines are together, the stronger the field.

Magnetic field lines always point away from a magnet’s north pole and toward its south pole.

The magnetic field All magnets

create a magnetic field in the space around them, and the magnetic field creates forces on other magnets.

3 Properties of All Magnetic Fields1. Similar poles of two magnets always repel each

other 2. Dissimilar poles of magnets always attract each

other 3. The two poles of a magnet are indivisible. The

broken magnets act as independent magnets and possess two poles each. It concludes that, magnets are always bipolar.

The ends of a magnet are where the magnetic effect is the strongest. These are called “poles.” Each magnet has2 poles – 1 north, 1 south.

If you cut a magnet in If you cut a magnet in half,half,

you get 2 magnets!you get 2 magnets!

3 Types of Magnets

1. Permanent: Difficult to magnetize but keep the magnetism

2. Temporary: easy to create a magnetic field but lose it quickly

3. Electromagnetic: magnet created with an electric current.

How To Make A Magnet?

Rub a magnet on a pin!

The Earth is a magnet:The Earth is a magnet:

Magnetic South Pole

Magnetic North Pole

It exerts magnetic forces and is surrounded by amagnetic field that is strongest near theNorth and South magnetic poles

William Gilbert, an English physician, first proposed in 1600 that the Earth itself is a magnet, and he predicted that the Earth would be found to have magnetic poles.

The Magnetic Field of the Earth As early as 500 B.C.

people discovered that some naturally occurring materials— such as lodestone and magnetite—have magnetic properties.

By 1200, explorers from Italy were using a compass to guide ocean voyages beyond the sight of land.

34

The Earth is a magnet

WHY??

NORTH POLE

Cornell Univ.

The Earth is made of four layers

The Crust:

A Thin Rock Material

The Mantle:

Dense rock

The Crust:

A Thin Rock Material

The Outer Core:

Liquid Iron and Nickel

The Mantle:

A Dense and Mostly Solid Rock Material

The Crust:

A Thin Rock Material

The Inner Core:

Solid Iron and Nickel

The Outer Core:

Liquid Iron and Nickel

The Mantle:

A Dense and Mostly Solid Rock Material

The Crust:

A Thin Rock Material

The Iron Core of the Earth is an Electromagnet

The Iron Core of the Earth is an electromagnet

The core is surrounded by liquid Iron and Nickel

The Iron Core of the Earth is an electromagnet

The core is surrounded by liquid Iron and Nickel

As electrons flow around the core the magnetic field

is produced

The Iron Core of the Earth is an electromagnet

The core is surrounded by liquid Iron and Nickel

As electrons flow around the core the magnetic field

is produced

The Earth’s rotation makes the electrons flow

at very high speeds

A little more info… The earth’s magnetic field isn’t strong

enough for us to feel, but many animals can sense it and even use it to navigate. It’s only about 0.4 Gauss, much weaker than a small magnet you can hold in your hand.

On average, the North & South poles “flip” every 390,000 years. There have been 9 flips in the past 3.5 million years.

Sometimes, Sometimes, the Earththe Earth’’s s magnetic magnetic poles flip. poles flip. This happens This happens every half-every half-million years million years or so.or so.

Magnetic North Pole

Magnetic South Pole

The poles “flip” ?

No one knows how long the process takes, maybe a few years, maybe a few minutes.

Every so often, what was the North magnetic pole suddenly becomes the South magnetic pole.

Lava that cools quickly on the sea floor records these flips and lets us date them.

Why do we care?

Earth’s magnetic field isn’t just “there” with no purpose. Without it, you and I and every living thing on this planet would be dead (including the cockroaches!)

The magnetic field channels away the solar wind.

It also prevents erosion of the atmosphere.

Solar Wind So what is the solar wind anyway? It’s radiation: extremely hot, high-energy, fast-

moving charged particles (ions) given off by the sun. Most of these particles are protons.

If you were exposed to it for just a few hours without protection, your skin and every organ in your body would be burned, and you’d have a fatal dose of radiation poisoning.

How does the magnetic field protect us? The magnetic field captures the solar wind

and channels much of it into a donut of radiation around the earth.

This donut (actually 2 layers – one inside the other) is called the Van Allen Radiation Belt (V.A.R.B.)

Where the magnetic field collapses inward, creates the Northern and Southern Lights

Where does the radiation go? Since the sun continually supplies new

solar wind, where does the solar wind go that the earth has already captured?

The magnetic field channels some of it into our atmosphere at the north & south poles. Here it ionizes oxygen and nitrogen atoms, causing the beautiful northern and southern lights.

The solar wind is constantly bombarding the Earth’s magnetic field. Sometimes these charged particles penetrate that field. These particles are found in two large regions known as the Van Allen Belts.

Where does the rest of the radiation go? Much of it flows through the magnetic field,

around the earth, and “drips” off the tail of the magnetic field. The tail is called the “magnetotail.”

Without our “Teflon-coating” of magnetic field, the earth would have been cooked many billions of years ago.

Northern Lights? The northern lights are properly called the

“aurora borealis.” They’re nothing more than a very large fluorescent light display (without the fluorescent tube!)

The northern lights are sometimes seen as far south as Florida, especially when the sun is very active.

The Earth’s magnetic field extends far into space. It is called the “magnetosphere.”

When the magnetic particles from the sun, called “solar wind”, strike this magnetosphere, we see a phenomenon called…

This aurora was photographed in Tennessee in October, 2002.

The Aurora Borealis in the Northern HemisphereThe Aurora Borealis in the Northern Hemisphere

And the Aurora Australis in the Southern HemisphereAnd the Aurora Australis in the Southern Hemisphere

The Magnetic Field of the Earth

Key Question:

How do we use Earth’s magnetic field to tell direction?

63

A compass uses a tiny magnet

which can swing round.If opposites attract, why doesa compass point north?

The Magnetic Field of the Earth When you use a compass, the

north-pointing end of the needle points toward a spot near (but not exactly at) the Earth’s geographic north pole.

The Earth’s magnetic poles are defined by the planet’s magnetic field.

That means the south magnetic pole of the planet is near the north geographic pole.

The North Pole of the Earth has a “south” polarity

S

N

As a result a compass will always point towards the North

S

N

S

N

N

S A compass is a Magnetized piece of metal that can spin.

A compass is a Magnetized piece of metal that can spin.

S

N

N

S

The north tip of the compass always points

towards the North Pole of the Earth

North attracts South

The Magnetic Field of the Earth

Depending on where you are, a compass will point slightly east or west of true north.

70

Using a compass to find directions A compass needle always points to the

Earth’s GEOGRAPHIC North Pole. Really the North pole is a South Magnetic pole

Some birds use the Earth’s magnetism to find directions.