Magnetism

1. Magnetism

2. 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

3. 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

6. 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.

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

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

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

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

11. 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

12. 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

13. 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

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

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

16. Magnetic variation • Magnetic poles of the Earth are different from the geographic poles of the Earth

17. Magnetic Induction • Process by which materials can be magnetized

22. 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

24. Electricity and Magnetism • Electric forces hold atoms and molecules together. • Electricity controls our thinking, feeling, muscles and metabolic processes. • Electricity and magnetism underpin much of our current technology (e.g. computers). • Electricity and magnetism are linked on a fundamental level.

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

26. 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

28. Increasing the strength of electromagnets • Increasing the voltage or current • Increasing the number of loops of wire

29. 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?

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

32. 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)

33. 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?