1. In this presentation you will:
Explore the concept of magnetism and magnetic fields.
ClassAct SRS enabled.

2. Magnets were first put to use to help navigate since they always point on the same direction.
But why do they behave that way?
In this presentation you will learn about magnetism and some properties of magnets.
Next >

3. Magnets
Magnets have the effect of influencing certain materials near to them.
An invisible force field surrounds a magnet that is capable of pushing or pulling certain objects.
The force field surrounding a magnet is known as a magnetic field.
Next >

4. Magnets
All materials can be magnetized under the effect of a magnetic field, but the effect is only easily seen in certain materials.
Steel
Iron
Materials that strongly exhibit this magnetic effect are called ferromagnetic.
Cobalt
Common ferromagnetic materials are iron, cobalt, nickel and steel. These materials are used to make permanent magnets.
Next >

5. Magnets
Ferromagnetic materials have magnetic domains that are like tiny magnets. These domains are randomly arranged and so cancel each other out.
Magnetic domain
When a ferromagnetic material is exposed to an external magnetic field, the domains in the material start to become more aligned, increasing the magnetic effect of the material.
If all of the magnetic domains are aligned in the same direction, the magnetic effect is at a maximum.
Next >

6. Magnets If a permanent magnet . . .
. . . is exposed to heat or vibration, the magnet can loose its magnetism.
This happens because the magnetic domains in the material start to become misaligned, decreasing the magnetic effect of the material.
Next >

7. Induced Magnets
Ferromagnetic materials fall into two categories: Hard and Soft.
Steel paperclips (Hard)
Iron nails (Soft)
Hard magnetic materials cannot be easily magnetized, but will retain their magnetism when the magnetizing field is removed.
When the external magnetic field is removed, the magnetic domains will stay partly aligned so the material remains slightly magnetic.
Next >

8. Induced Magnets
Soft magnetic materials can be easily magnetized, but quickly lose their magnetism when the magnetizing field is removed.
These materials are used to make temporary magnets and they are commonly used in cores for transformers and electromagnets.
Iron nails (Soft)
Steel paperclips (Hard)
Next >

9. Question 1
Which of the following is NOT a magnetic material that permanent magnets can be manufactured from?
A) Iron
B) Aluminum
C) Cobalt
D) Nickel

10. Magnetic Poles
If the end of a magnet is free to move, it will always point toward the Earth's geographical North Pole.
This end is known as a north-seeking pole or, more simply, as a North Pole.
The other end of a magnet is called a South Pole. This is the basis of a magnetic compass.
Next >

11. Attraction and Repulsion
The Law of Magnetic Poles states that:
Unlike poles of two magnets brought close together will attract each other.
Like poles will repel each other.
Next >

12. Magnetic Field
The magnetic field is the region surrounding a magnet where the magnetic force can be detected.
A compass can be used to map out the magnetic field around a magnet by recording the direction that a compass points at different positions around the magnet.
Next >

13. Magnetic Field
If a magnetic field is strong enough, it can be mapped using iron filings.
The field is made up of lines of flux or force. These lines are closer together where the field is strongest, at the poles.
To retain a magnetic field and make a permanent magnet, a hard magnetic material such as steel is required.
Next >

14. Magnetic Field
The diagram below shows the magnetic field surrounding a magnet. It can be seen that the field goes from the north pole to the south pole.
The lines are closest together at the poles, indicating that the magnetic field is strongest at the poles.
Next >

15. Question 2
Magnetic field lines are formed around a magnet. Technician A says the lines are known as lines of flux. Technician B says the lines show the force. Who is correct?
A) Technician A only.
B) Technician B only.
C) Both technician A and technician B.
D) Neither technician A nor technician B.

16. Question 3
If two magnets are pushed together at their opposite (unlike) poles, will they attract each other?
Answer Yes or No.

17. Summary After completing this presentation you should be able to:
Show knowledge and understanding of magnetism.
Show knowledge and understanding about induced magnets.
Show knowledge and understanding about magnetic fields.
End >