1. Learning Objectives
I can explain what magnetic poles and magnetic field are & what causes them to exist.
I can tell why some materials are magnetic and some are not.
I can tell how domains can cause materials to be magnetic.
I can explain how Earth acts as a magnet and how Earth’s geographic & magnetic poles differ.

2. Ohio New Learning Standards for Science
Ohio 8th Grade, Physical Science #1 (8.PS.1) – Forces between objects act when the objects are in direct contact or when they are not touching.

3. Lesson Opener      
This magnet sits inside a cow’s stomach & attracts and holds metal objects near it. The magnet protects the cow’s system.
An open area of ground.
The area surrounding a magnet.

4. Unit 7, Lesson 4 – Magnets and Magnetism
What are some properties of magnets?
- magnets are any materials that attract iron or objects made of iron
- most magnets are made from iron, nickel, cobalt, or gadolinium
iron
nickel
cobalt
gadolinium

5. Unit 7, Lesson 4 – Magnets and Magnetism
- when you bring two magnets together, they exert a push or a pull called a magnetic force on each other
- this force results from spinning electric charges in the magnets
- this force can either push magnets apart or pull them together
Pulling Force
Pushing Force

6. Unit 7, Lesson 4 – Magnets and Magnetism
- there are only three forces in the Universe that can act at a distance by pushing or pulling: magnetic force, electrostatic force, and gravity
magnetic force
electrostatic force
gravitational force
Complete #5 & #6, pg.446

7. Unit 7, Lesson 4 – Magnets and Magnetism
push or pull
The pull of the magnet is concentrated to one side so it can easily be used to pick things up.

8. Unit 7, Lesson 4 – Magnets and Magnetism
- all magnets have two ends called magnetic poles, which are designated as either “north” or “south”
- like poles repel each other, whereas opposite poles attract each other (opposites attract!)

9. Unit 7, Lesson 4 – Magnets and Magnetism
- the area surrounding a magnet where magnetic forces can be detected is called the magnetic field
- the strongest parts of the magnet are the poles!
Complete #7 & #8, pg.447

10. Unit 7, Lesson 4 – Magnets and Magnetism
The lines are closest together near the poles, showing that the force is strongest there. O X

11. Unit 7, Lesson 4 – Magnets and Magnetism
What causes magnetism?
- as an electron moves in an atom, it makes, or induces a magnetic field
- the electron will then have a north & south magnetic pole
- most elements’ atoms have electrons that cancel each other out magnetically, so they are NOT magnetic

12. Unit 7, Lesson 4 – Magnets and Magnetism
- the magnetic fields of iron, nickel, cobalt, and gadolinium atoms do not completely cancel each other out, so all the atoms have small magnetic fields
- therefore, this is why the smallest magnets we can create still have north & south poles!
- in materials like iron, nickel, cobalt, & gadolinium, groups of atoms form tiny areas called domains (north & south pole domains line up & make strong magnetic fields

13. Unit 7, Lesson 4 – Magnets and Magnetism
- when a magnetic material is placed in a magnetic field, most of the domains point toward the same direction, forming a field around the object
Complete #9, pg.448
The domains in the unmagnetized nail are pointing in different directions. The domains in the magnetized nail are mostly pointing in the same direction!

14. Unit 7, Lesson 4 – Magnets and Magnetism
What are some types of magnets?
- some materials are naturally magnetic, like magnetite, but others can become temporary magnets
- a material that can be turned into a magnet is called ferromagnetic (iron, nickel, cobalt, gadolinium are excellent examples!)
- ferromagnetic materials can be made into permanent magnets, that hold their properties longer

15. Unit 7, Lesson 4 – Magnets and Magnetism
- strong magnets used to pick up very heavy objects are called electromagnets
- electromagnets are iron cores wrapped with electrical wire
- the greater the electrical current, the stronger the electromagnet!

16. Unit 7, Lesson 4 – Magnets and Magnetism

17. Unit 7, Lesson 4 – Magnets and Magnetism
- some materials, such as soft iron, can be made into temporary magnets
- rubbing a magnet on some metal materials aligns their magnetic domains temporarily

18. Unit 7, Lesson 4 – Magnets and Magnetism
How is Earth like a giant magnet?
- because Earth is primarily made of molten iron in the outer core, it has an enormous magnetic field
- as the Earth rotates, the liquid outer core moves
- charged particles, including electrons, move in the liquid and form a magnetic field
- the constant rotation keeps Earth magnetized!

19. Unit 7, Lesson 4 – Magnets and Magnetism
- Earth’s magnetic field is strongest near its poles
- the magnetic poles are close to the geographic poles indicated on maps
- therefore, why does the north end of a compass point to the north geographic pole????
Complete #12, pg.450 & #13, pg.451

20. Unit 7, Lesson 4 – Magnets and Magnetism
The moving outer core of Earth would change the position of the magnetic pole over time. N

21. Unit 7, Lesson 4 – Magnets and Magnetism
- like forces repel and opposites attract, so the north end of a compass needle has to be attracted to a south polarized magnet, which is located near the geographic north pole!

22. Unit 7, Lesson 4 – Magnets and Magnetism
What is an aurora?
- the Aurora Borealis (Northern Lights) and the Aurora Australis (Southern Lights) are caused by charged photons being attracted to the poles
- when the charged photons interact with the air molecules in the atmosphere, the atoms give off visible light which glows

23. Visual Summary forces fields poles ferromagnetic domains electromagnet
temporary
magnetic field
magnetic poles

24. Exit Question How can a compass be used to find geographic north?
The “north-seeking” pole of the compass needle is magnetically attracted to the south magnetic pole, which is very close to the geographic North Pole.