1. Preview Section 1 Magnets and Magnetism
Electromagnetism
Preview
Section 1 Magnets and Magnetism
Section 2 Magnetism from Electricity
Section 3 Electricity from Magnetism
Concept Mapping

2. Objectives Describe the properties of magnets.
Section 1 Magnets and Magnetism
Objectives
Describe the properties of magnets.
Explain why some materials are magnetic and some are not.
Describe four kinds of magnets.
Give two examples of the effect of Earth’s magnetic field.

3. Section 1 Magnets and Magnetism
Properties of Magnets
Magnetic Poles are points on a magnet that have opposite magnetic qualities.
Magnet – anything that attracts iron or things made of iron.
North and South The pole of a magnet that points to the north is called the magnet’s north pole. The opposite end of the magnet, called the south pole, points to the south. Poles always come in pairs.
The pointer of a compass is actually a small magnet.

4. Section 1 Magnets and Magnetism
Properties of Magnets
When two magnets get close together, each exerts a magnetic force on the other.
Magnetic force:
Either push or pull. Opposites attract./pull
Caused by spinning electric charges in the magnets.
Magnetic forces are universal – always happen when poles get close

5. Section 1 Magnets and Magnetism

6. These lines are called “field lines.”
Section 1 Magnets and Magnetism
Magnetic Fields A magnetic field exists in the region around a magnet in which magnetic forces can act.
These lines are called “field lines.”

7. Properties of Magnets, continued
Section 1 Magnets and Magnetism
Properties of Magnets, continued
These “field lines” emerge from the magnet’s north pole and are pulled toward the south pole.

8. Properties of Magnets, continued
Section 1 Magnets and Magnetism
Properties of Magnets, continued
These “field lines” emerge from the magnet’s north pole and are pulled toward the south pole.

9. The Magnetosphere: the Magnetic Field around the Earth.
Section 1 Magnets and Magnetism
The Magnetosphere: the Magnetic Field around the Earth.
Here it’s shown being deflected/pushed by energy from the sun – the solar wind.

10. Each domain is like a tiny magnet.
Section 1 Magnets and Magnetism
The Cause of Magnetism
Atoms and Domains
In iron, nickel, and cobalt, atoms are grouped in tiny areas called domains.
Each domain is like a tiny magnet.
When the atoms in domains line up, you get a stronger magnetic field.

11. Section 1 Magnets and Magnetism

12. Section 1 Magnets and Magnetism
The Cause of Magnetism
If The north and south poles of the atoms in a domain DON’T line up, no strong magnetic field.
Atoms in domains can be lined up using another magnet, creating or recreating a magnetic field.

13. Section 1 Magnets and Magnetism

14. The Cause of Magnetism, continued
Section 1 Magnets and Magnetism
The Cause of Magnetism, continued
Losing Alignment When domains move and get more random, the magnet is demagnetized. It loses its magnetic properties.
Making Magnets You can remagnetize demagnetized material if you realign its domains using another magnet.
When a paper clip is attracted to a magnet, it actually becomes a magnet for a short time.

15. The Cause of Magnetism, continued
Section 1 Magnets and Magnetism
The Cause of Magnetism, continued
Cutting a Magnet When you cut a magnet in half, you end up with two magnets.

16. Electromagnets: a magnet created by an electric current.
Section 1 Magnets and Magnetism
4 Kinds of Magnets
Ferromagnets: are made of iron, nickel, cobalt, or mixtures of those metals.
Electromagnets: a magnet created by an electric current.
Temporary magnets: made from materials that are easy to magnetize. But lose their magnetization easily.
Permanent magnets: difficult to magnetize, but tend to keep their magnetic properties longer.

17. Section 1 Magnets and Magnetism
Earth as a Huge Magnet!!
One Giant Magnet Earth behaves as if it has a bar magnet running through its center.
Poles of a Compass Needle Opposites attract. A magnet’s north pole is attracted to south poles.
South Magnetic Pole near North Geographic Pole A compass needle points north because the magnetic pole of Earth that is closest to the geographic North Pole is a magnetic south pole.

18. Section 1 Magnets and Magnetism

19. Earth as a Magnet, continued
Section 1 Magnets and Magnetism
Earth as a Magnet, continued
The Core of the Matter Scientists think that the Earth’s magnetic field is made by the movement of electric charges of electrons in the liquid iron as it flows in the Earth’s outer core.
Flow of Electrons! Electricity!
A Magnetic Light Show Earth’s magnetic field plays a part in making auroras. An aurora ( Northern Lights) is formed when charged particles from the sun hit oxygen and nitrogen atoms in the air.

20. Section 2 Magnetism from Electricity
Objectives
Identify the relationship between an electric current and a magnetic field.
Compare solenoids and electromagnets.
Describe how electromagnetism is involved in the operation of doorbells, electric motors, and galvanometers.

21. Hans Christian Oersted Danish physicist.
Section 2 Magnetism from Electricity
The Discovery of Electromagnetism
Hans Christian Oersted Danish physicist.
In 1820 discovered the relationship between electricity and magnetism in 1820.

22. Section 2 Magnetism from Electricity
The Discovery of Electromagnetism
Found that electric current produces a magnetic field.
First research in electromagnetism — the interaction between electricity and magnetism.

23. Section 2 Magnetism from Electricity

24. ELECTROMAGNET: solenoid wrapped around an iron core.
Section 2 Magnetism from Electricity
Using Electromagnetism
SOLENOID: the coil of wire that produces a magnetic field when carrying an electric current.
ELECTROMAGNET: solenoid wrapped around an iron core.

25. Section 2 Magnetism from Electricity
Using Electromagnetism
The solenoid has a magnetic field only when there is electric current in it.
Magnetism in electromagnets can be turned on and off by turning the electricity in the solenoid on or off.

26. Applications of Electromagnetism
Section 2 Magnetism from Electricity
Applications of Electromagnetism
Doorbells Two solenoids in a doorbell allow the doorbell to work.
Magnetic Force and Electric Current An electric current can cause a compass needle to move. The needle is a small magnet. This property is useful in electric motors.

27. Applications of Electromagnetism
Section 2 Magnetism from Electricity
Applications of Electromagnetism

28. Section 2 Magnetism from Electricity
Applications of Electromagnetism, continued
Electric motor: a device that changes electrical energy into mechanical energy.
All electric motors have an armature—a loop or coil of wire that can rotate.

29. Galvanometers: measures electrical current.
Section 2 Magnetism from Electricity
Applications of Electromagnetism, continued
Galvanometers: measures electrical current.
Uses an electromagnet placed between the poles of a permanent magnet.

31. Objectives Explain how a magnetic field can make an electric current.
Section 3 Electricity from Magnetism
Objectives
Explain how a magnetic field can make an electric current.
Explain how electromagnetic induction is used in a generator.

32. Electric Current Created From a Changing Magnetic Field
Section 3 Electricity from Magnetism
Electric Current Created From a Changing Magnetic Field
Faraday’s Experiment
Michael Faraday: Tried to get the magnetic field of an electromagnet to make an electric current in a second wire.

33. Section 3 Electricity from Magnetism

34. Faraday succeeded in “inducing” electric current in the second wire.
Section 3 Electricity from Magnetism
Faraday succeeded in “inducing” electric current in the second wire.
Electrical current induced only when the magnetic field changed or moved by moving the magnet.

35. Section 3 Electricity from Magnetism
This process, where an electric current is made by changing a magnetic field is called electromagnetic induction.
Inducing Electric Current Look at the next slide to see electromagnetic induction.

37. Section 3 Electricity from Magnetism
Electric Generators
Alternating Current (AC) The electric current produced by the generator shown on the next slide changes direction each time the coil makes a half turn. Because the electric current changes direction, it is an alternating current. Household current is AC.
Generating Electrical Energy The mechanical energy that generators convert into electrical energy comes from different sources such as fossil fuels and nuclear energy.

38. Coil/wire crosses mag. field lines
Bulb ON

39. Section 3 Electricity from Magnetism
Transformers
A transformer increases or decreases the voltage of alternating current.
Transformers have two coils of wire: primary and secondary. Coils are close, but do not touch.
Primary coil: side where current comes in
Secondary coil: side where current goes out

40. Transformers Primary coil: Side where current comes in.
Section 3 Electricity from Magnetism
Transformers
Primary coil:
Side where current comes in.
Current in the coil creates magnetic field there.
This magnetic field reverses when direction of current reverses. (AC, remember?)

41. Transformers Secondary coil:
Section 3 Electricity from Magnetism
Transformers
Secondary coil:
Influenced by the primary coil’s magnetism
The back-and-forth switching of direction of the magnetic field on the primary side moves the electrons in the secondary coil back and forth.
This movement is electricity, by EM induction.
The electricity leaves the secondary coil.

42. Section 3 Electricity from Magnetism
More coils = more juice!
Compare the # loops in primary and secondary to figure out if step up or step down. Secondary coil determines which.
Step Up Transformer: causes voltage to increase, step up.
Secondary coil has more loops than the primary
Step Down Transformer: causes voltage to decrease, step down. Secondary coil has fewer loops than the primary

44. Electromagnetism
Concept Mapping
Use the terms below to complete the concept map on the next slide.
mechanical energy electrical energy
electromagnetic induction electric motor
transformers
voltage

45. Electromagnetism

46. Electromagnetism