Magnets and Magnetism
• In this presentation you will see:
• What magnets are. • Magnetic poles and fields. • Different types of magnets. • Uses for magnets.
What a magnet is…
• A stone or piece of metal that has the ability to pull or attract certain things towards itself.
What a magnet is…
• Magnets attract only the things which have the metals iron, nickel or cobalt in them.
What a magnet is…
The pull or force of a magnet is called magnetism.
What is a Magnet?
• If a magnet is broken in two, each piece continues to be a magnet.
What is a Magnet? • We are unable to break magnets into small enough pieces to have those pieces not display the properties of magnetism.
Why are some materials magnetic? • Scientists believe that metals contain molecules called dipoles.
Why are some materials magnetic? • In unmagnetized metals these dipoles are arranged in a random order.
Why are some materials magnetic?
• In magnetized metals these molecules line up in a pattern called a domain.
Nucleus
Why are some materials magnetic? • Scientists also explain magnetism as being caused by the motion of electrons.
Electrons
Why are some materials magnetic?
Nucleus
Electrons
• Inside most atoms electrons spin around the center of the atom in all different paths, without running into each other.
Why are some materials magnetic? • In magnetized pieces of iron, nickel, and cobalt, the electrons of the atom almost all spin in the same direction around the center of the atom.
Why are some materials magnetic? • Scientists say that these spinning electrons set up a current which is magnetism.
Magnetic Poles and Fields
• A Magnet has two different ends or poles.
Magnetic Poles and Fields • They are called the north and south magnetic poles.
Magnetic Poles and Fields
• The earth itself is a giant magnet.
Magnetic Poles and Fields • The south magnetic pole attracts the south seeking pole of every magnet in the world.
Magnetic Poles and Fields • The north magnetic pole of the earth attracts the north-seeking pole of every magnet in the world.
Magnetic Poles and Fields • Around every magnet there is a space about which its force will work. This space is called the magnetic field of the magnet.
Magnetic Poles and Fields • The force of the magnet reaches out in lines. These lines are called lines of force.
Magnetic Poles and Fields • The magnetic field of a magnet is strongest near the poles of that magnet and weaker near the center of the magnet.
Two Different Types of Magnets
There are two different kinds of magnets:
• Natural • Artificial
Two Different Types of Magnets
• Natural magnets are stones which have the ore magnetite in them.
Two Different Types of Magnets • These stones are called lodestones. • Lodestones are found in the earth.
Two Different Types of Magnets
• Artificial magnets are made by people.
Two Different Types of Magnets • Artificial magnets are used much more today than natural magnets because they can be made into different shapes and are much stronger.
Temporary and Permanent Magnets
• There are temporary and permanent Magnets.
Temporary and Permanent Magnets • A temporary magnet is a one which will lose its magnetism quickly.
Temporary and Permanent Magnets
• A permanent magnet is one which will keep its magnetism for a long time.
Temporary and Permanent Magnets
• Temporary Magnets can be made by: • Physical contact - Rub, in 1 direction, a piece of iron, cobalt or nickel with a magnet. • Physical contact - Touch, and remain in contact with a piece of iron, cobalt or nickel.
Temporary and Permanent Magnets
• Temporary Magnets can be made by: • Physical contact - Rub, in 1 direction, a piece of iron, cobalt or nickel with a magnet. • Physical contact - Touch, and remain in contact with a piece of iron, cobalt or nickel.
Temporary and Permanent Magnets
• Permanent Magnets can be made by: • Wrapping insulated wire around a piece of iron, nickel or cobalt. When a strong electric current is passed through the wire, the metal will become a permanent magnet. • The metal will remain magnetic for a period of several years.
Electromagnets
• These are the most useful kinds of magnets. • Are made by passing current through a wire. • Are the strongest types of magnets. • Are temporary magnets • Can be made stronger by adding more coils, more current.
Uses of Magnets
• Tools: Magnetic tools help hold or capture tiny pieces of metal or hold things closed or open. • Direction: The magnetic compass has been used for thousands of years to find direction. • Electricity: Magnets are used in generators to produce the words energy. • Motors: Magnets are used inside motors to cause movement. • Separating Processes: Magnets can be used to remove metal from nonmetals.