Magnetism

What is magnetism? Force of attraction or repulsion due to electron arrangement Magnetic forces are the strongest at the poles Magnets have two poles: North and South

Magnetic poles and fields Magnets always have two poles If a magnet is cut it will still have two poles Like magnetic poles repel Unlike magnetic poles attract A magnetic field is the area in which magnetic forces act

Questions What two forces are involved in magnetism? Which subatomic particle accounts for magnetism? Explain the interaction between magnetic poles when they are close together.

Magnetic materials Natural magnets have naturally occurring magnetic properties ex: LODESTONE (magnetite)

Temporary magnets Easy to magnetize Lose their magnetism quickly Ex: Soft iron

Permanent magnets Hard to magnetize Stay magnetized longer than temporary magnets Ex: alnico (cobalt, nickel, aluminum)

Questions How is a temporary magnet different from a permanent magnet? Give an example of a natural magnet.

Earth’s magnetic properties Gilbert was a scientist that showed that the Earth behaves as a magnet The Earth’s magnetic field is strongest at the poles Earth’s magnetic field is called the magnetosphere

Compasses Compasses are used to determine direction Compass needles are magnetized and respond to the magnetic field of the Earth Compasses point to the MAGNETIC POLES OF THE EARTH

Other sources of magnetism Magnetic fields of the Earth and other planets are related to their cores The sun is a source of a magnetic field

Questions Which scientist described the Earth’s magnetic properties? Name the devices used to indicate geographic direction based on the Earth’s magnetic field.

Questions What is the name of the Earth’s magnetic field? Where is the Earth’s magnetic field the strongest?

Magnetic variation Magnetic poles of the Earth are different from the geographic poles of the Earth

Magnetic Induction Process by which materials can be magnetized

What affects magnetic properties? Spinning electrons cause some metals to have magnetic properties Magnetic domains are groups of arranged magnetic fields Dropping,hammering or heating a magnet will cause a magnet to lose magnetic properties

Electromagnetism Discovered by Oersted (scientist) Relationship between electricity and magnetism

Electromagnets Temporary magnets Magnetism can be turned on and off Made by wrapping wire around a piece of iron and sending a current through the wire Magnetic field is in the same direction as the electric current

Increasing the strength of electromagnets Increasing the voltage or current Increasing the number of loops of wire

Questions Explain magnetic variation. What is electromagnetism? Who discovered electromagnetism? Name two ways to increase the strength of an electromagnet. What type of magnet is an electromagnet?

Electric motors vs. generators Electric motors convert electricity to mechanical energy in order to do work Generators convert mechanical energy to electrical energy

Transformers Used to increase or decrease voltage Made of primary and secondary coils Two types of transformers: “Step-up” (increase voltage) “Step-down”(decrease voltage)

Questions How is a generator different from an electric motor? Name two types of transformers. How is a step-up transformer different from a step down transformer? What are the two parts of a transformer?