MAGNET NOTES!

• Over 2,000 years ago, Greeks discovered a mineral that attracted things made of iron

• Found in a part of Turkey called Magnesia, so they called it Magnetite

HISTORY OF MAGNETS

MAGNETIC PROPERTIES• Magnetic Poles

• Magnetic Forces

• Magnetic Fields

• Magnetic Poles

• Every magnet has a north and south pole-points on a magnet that have opposite magnetic qualities

• Magnetic Forces–The force of

attraction or repulsion magnets exert on each other

PROPERTIES OF MAGNETS

• Examples of Repulsion: • Example of Attraction:

ATTRACTION/REPULSION

• The region around a magnet in which magnetic forces can act.

MAGNETIC FIELDS

WHAT ARE THE ATOMS INSIDE OF A MAGNET DOING?

• As negatively charged electrons move around, they make, or induce, a magnetic field.

• In most material the magnetic field of individual atoms cancel each other.

• In some materials the north and south poles line up in a domain (place where groups of atoms are found).

• If most of the domains in an object align they can combine to make an entire object magnetic.

WHAT DOES THE INSIDE OF A MAGNET LOOK LIKE?

Inside a non-magnetic object Inside a magnetic object

• A magnet is any material that attracts iron or things made of iron.

WHAT IS A MAGNET?

CAN MAGNETS BE DEMAGNETIZED?

• When a magnet’s domains move, the magnet is demagnetized and loses its magnetic properties.

• This can be done by:

• Dropping a magnet

• Hitting it too hard

• Putting a magnet in a strong magnetic field that is opposite to its own

• Increasing the magnet’s temperature-with a higher temperature, atoms vibrate faster and the atoms in the domains may no longer line up

• Line up the domains by rubbing the object with one pole of a magnet

• Domains in the object will line up with the magnetic field of the magnet

• This is why a magnet can pick up an unmagnetized object like paper clips

• When a magnet is close to the paper clip, some of the domains in the paper clip line up with the field of the magnet.

• When the magnet is removed, the paper clip’s domains become scrambled again.

MAKING A MAGNETTo make a magnet out of something made of iron, cobalt, or nickel:

• Difficult to magnetize and keep their magnetic properties longer than temporary magnets.

• Some permanent magnets are made with alnico-an alloy made up of aluminum, nickel, cobalt, and iron.

• Made from materials that are easy to magnetize, but lose their magnetism easily.

• Soft iron is iron that has not been mixed with any other materials and can be made into temporary magnets

• The paper clip and nail in the mini-lab were temporary magnets.

KINDS OF MAGNETS

Temporary Magnets Permanent Magnets

WHAT WOULD HAPPEN IF YOU CUT A MAGNET?

• Would you end up with one north pole and one south pole?

• NO

• When you cut a magnet, you get two magnets, each with its own north and south pole.

• Why?

• A magnet has poles because its domains are lined up, and each domain is like a very tiny magnet with a north and south pole, so even the smallest pieces of a magnet have a north and south pole.

MAGNETIC FIELD NOTES

• Region around a magnet in which magnetic forces can act

• Shape is shown with lines drawn from the north pole of the magnet to the south pole, called magnetic field lines

• The closer together the magnetic field lines are the stronger the magnetic force is

• What part of the magnet has the strongest magnetic force? How can you tell?

• AT THE POLES – magnetic field lines are closest together!

MAGNETIC FIELDS

Two Like Poles Two Opposite Poles

MAGNETIC FIELD INTERACTIONS

• Scientists think that the earth’s magnetic field is made by the movement of electric charges in the Earth’s liquid outer core, which is made out of iron and nickel.

• When the Earth rotates, the liquid in the core flows

• When the liquid flows, electric charges move, which makes a magnetic field

THE EARTH AS A MAGNET.

• How does a compass work?

• The compass needle points north because its north pole is attracted to the earth’s magnetic south pole.

• What does this mean then?

• The earth has a very strong magnetic field

USING A COMPASS

• Auroras are made by charged particles from the sun hitting oxygen and nitrogen atoms in the air.

• The atoms become excited and give off light

• Auroras at north pole are called northern lights, or aurora borealis

• Auroras at south pole are called southern lights, or aurora australis

NORTHERN/SOUTHERN LIGHTS

WHY ARE AURORAS ONLY AT THE POLES?