Magnets & Magnetism Unit 11 Section 1

I. Magnets A magnet is any material that attracts iron or materials containing iron, like steel. Characteristics of all magnets: Have two poles (north & south) Exert forces on each other Surrounded by a magnetic field

II. Magnetic Poles At the end of each magnet is a magnetic pole. Magnetic poles are points on a magnet that have opposite magnetic qualities. The pole of a magnet that points north is the magnet’s NORTH POLE. The pole of a magnet that points south is the magnet’s SOUTH POLE.

III. Magnetic Forces a.) Magnetic force is the force of attraction (come together) or repulsion (push away) generated by moving or spinning electric charges. b.) When magnets are brought closer to each other, like poles will repel and opposite poles will attract - this is because of magnetic force. north and south poles will attract. south and south poles or north and north poles will repel. (Sound familiar?)_____

IV. Magnetic Field A magnetic field is the area around a magnet in which the magnetic forces can act. You can see a magnetic field by sprinkling iron filings around a magnet.

V. What is the cause of magnetism? The material’s atoms determine if the material can be magnetic. All matter is made of atoms. Electrons are negatively charged particles of atoms. As the electrons move around, they create a magnetic field.

VI. Domains In magnetic materials, such as iron, cobalt and nickel, groups of atoms are in tiny areas called domains. Domains are like tiny magnets of different sizes within an object. If the domains in an object are randomly arranged, the magnetic fields of the individual domains cancel each other out, and the object has no magnetic properties. If most of the domains in an object are aligned (all facing the same way), the magnetic fields of the individual domains combine to make the whole object magnetic.

VII. Making a Magnet You can make a magnet from objects made of iron, cobalt or nickel. The domains in the object need to align (line up) with a magnet. Example: You can magnetize an iron nail if you rub it in one direction with one pole of a magnet. The domains align with the magnetic field of the magnet, making the nail a magnet. Example: When a magnet is close to a paperclip, some domains in the paperclip line up with the field of the magnet, making it a temporary magnet. When the magnet is removed, the domains in the paperclip become scrambled again.

VIII. Losing Alignment Sometimes a magnet can lose it’s magnetism or it can become demagnetized. This occurs when the domains don’t stay lined up. This would make a magnet lose it’s magnetic properties. This can happen when: A magnet is dropped High temperatures Putting the magnet in a strong magnetic field.

IX. Types of Magnets a. Ferromagnets: magnets made of iron, nickel, cobalt or mixtures of these materials. b. Electromagnets: magnets made by an electric current. These magnets usually have an iron core. c. Temporary magnets: can be created easily, but lose their magnetism quickly. Ex: soft iron d. Permanent magnets: can be difficult to create, but hold their properties longer. Ex: magents made with alnico.

X. Earth as a Magnet Earth acts as if it has a bar magnet through its center. Earth’s magnetic field is caused by the movement of electric charges in the Earth’s liquid core.

Why does a compass point North? The compass needle is a magnet - it is attracted to Earth’s magnetic south pole. Earth’s magnetic south pole is closest to the geographic North Pole (actual location on Earth if you were to fly there). This is why a compass points north. Extra info-this is because every 10,000 years or so, Earth’s core settles and then rearranges (like stirring a boiling pot of water). This causes the poles to switch.

Quickie Quiz The ends of the magnet are called ends tips poles current

Quickie Quiz The ends of the magnet are called ends tips poles current

Quickie Quiz Poles that are alike will __________ and poles that are opposite will _________ attract/repel repel/push away repel/attract none of the above

Quickie Quiz Poles that are alike will __________ and poles that are opposite will _________ attract/repel repel/push away repel/attract none of the above

Quickie Quiz Which is NOT a way a magnet loses its magnetism? A magnet is dropped High temperatures Putting the magnet in a strong magnetic field. Putting it in cold

Quickie Quiz Which is NOT a way a magnet loses its magnetism? A magnet is dropped High temperatures Putting the magnet in a strong magnetic field. Putting it in cold

Quickie Quiz Which of the following would NOT be attracted to a magnet? A copper penny An iron nail A steel bar A steel paperclip

Quickie Quiz Which of the following would NOT be attracted to a magnet? A copper penny An iron nail A steel bar A steel paperclip

Quickie Quiz The magnetic north pole of earth is Geographic north pole Attracted to the south pole of a magnet Attracted to the north pole of a magnet None of the above

Quickie Quiz The magnetic north pole of earth is Geographic north pole Attracted to the south pole of a magnet Attracted to the north pole of a magnet None of the above

Quickie Quiz What do you think would happen if you broke a bar magnet in half? You would get two smaller magnets, each with a north and south pole. You would get a magnet with a north pole, and one with a south pole. Neither “a” or “b”

Quickie Quiz What do you think would happen if you broke a bar magnet in half? You would get two smaller magnets, each with a north and south pole. You would get a magnet with a north pole, and one with a south pole. Neither “a” or “b”