MAGNETISM

The Earth Magnetic Poles North and South Geographic Poles North and South Earth is a giant magnet.

Magnetic Declination

Inclinometer An example of an inclinometer showing the Earth’s magnetic inclination

Compass Points The direction of compass points in United States

Types of Magnets LOADSTONE BAR U COIL ALNICO

Natural Magnet Material is Magnetite or Iron Oxide (Fe )

Magnets A very strong magnet can be made with a coil of wire and the flow of an electric current.

Alnico An extremely strong Alnico permanent magnet with keeper

Theory of Magnetism Molecular and Electron Theories

Creating Magnets The picture shows that a screwdriver does not pick up paper clips. Methods used to create a magnet

Creating Magnets Stroking using a permanent magnet However, after stroking the screwdriver with a magnet, the blade itself becomes magnetic and attracts the paper clips.

Flux Magnetic lines of force Strongest at the poles

Removing Magnetism Heat is one way to remove magnetism.

Laws of Magnets Poles attract or repel

Like Poles Repel

Laws of magnets shown by flux lines Unlike poles attractLike poles repel

Stray Lines of Force Controlling stray lines using a keeper

Magnetic Lines of Force Notice how the materials are affected Soft iron is a material that distorts flux Magnetism will pass through any material

Electromagnetism

Electromagnets A 30-foot diameter electromagnet used in research for a superconductor A large electromagnet used to lift scrap metal

Electromagnets The source of electromagnetism is electricity (current) flowing through a coil of wire.

Electromagnets A coil of wire can be made into a magnet by passing an electric current through it. Without electricity, there is no magnetic force Electric current applied to a coil creates a magnetic field

Electromagnetic Strength Increase the number of coils. Increase the electric current flowing through the coil. Add an iron core in the center of the coil. How can an electromagnet be made stronger?

Electromagnetic Strength

The left hand rule to determine North Pole NORTH POLESOUTH POLE

Making a Magnet An example of a very strong magnet

The magnet is strong enough to lift this 50 pound engine cylinder head. The coil of wire has been attached to a 12 volt DC power source making an extremely strong magnet. Making a Magnet

Saturation Saturation Knee Y- Axis Increasing Magnetic Force Y X- Axis Increasing Electric Current X Saturation of a magnetic field occurs when an increase of electric current flow does not increase the strength of the magnetic field as shown by the graph. The knee of the curve is the point that saturation occurs.

MAGNETIC COIL LOSSES Copper losses - resistance of copper coils. Hysteresis - magnetic flux inducing a current in the core. Eddy currents - magnetic polarity of the iron core is rapidly changed by an AC current causing friction and heat between the molecules

ELECTROMAGNETIC DEVICES

Electromagnetic Devices

MAGNETIC TERMS Flux - Invisible lines of force. Poles - North and South where force is strongest. Permeability – The ability of a material to conduct lines of force. Residual Magnetism – The ability of a material to hold its magnetism for a long time.

MAGNETIC TERMS Ferromagnetic Material – A material easy to magnetize. (i.e., Iron Steel, Cobalt, Perm-alloy, and Alnico) Paramagnetic Material- A material that can be slightly magnetized. Diamagnetic Material – A material that is very difficult to magnetize. Magnetic Laws – Simply stated: Like poles repel and unlike poles attract.

Review What are the poles of a magnet? Name the magnetic lines of force. List five types of magnets and their two families. List the laws of magnets. Explain two methods for making a magnet.

Review Explain two theories of magnetism. Name five different types of devices that are associated with electromagnetism? List three magnetic and three nonmagnetic materials. What will remove magnetic lines of force?