2. Variables: factors that can be controlled or changed in an experiment.
There are two important types
dependent and independent.

3. An ___________variable's values are controlled or selected by the experimenter to determine its relationship to an observed phenomenon (the _________variable)

4. An independent variable's values are controlled or selected by the experimenter to determine its relationship to an observed phenomenon (the dependent variable)

5. A B

6. Magnetism
Global Science

7. Think
What are magnets?

8. Magnetism Some materials are naturally magnetic. Lodestones: Naturally
                                                        
Some materials are naturally magnetic.
Lodestones: Naturally
occurring magnetic
rocks
The word magnet comes
from lodestones found in
Magnesia, Turkey

9. Magnets exert magnetic forces
Magnets can be permanent or temporary
Permanent magnet: retains its magnetic properties for a long time.
Temporary magnet: acts as magnet only as long as it is in the magnetic field produced by a permanent magnet or an electric current.

10. Magnets exert magnetic forces
Electromagnet: a type of magnet whose magnetic field is produced by the flow of electric current.
The magnetic field disappears when the current ceases.
Electromagnets are used as components of other electrical devices, such as motors, generators, loudspeakers, hard disks, MRI machines, etc…

11. Magnets exert magnetic forces
Electromagnet:
Wire is coiled around a piece of magnetic material and electric current is passed through the wire
The more coils (loops), the stronger the magnet

12. Magnets have poles Magnets have 2 poles a north and south
These poles exert a force on one another.
Two like poles (north, north)
repel each other,
while two unlike poles (north, south)
attract one another.
Question: What else exhibits this type of behavior?

13. Magnetic Fields A force is a . . . push or a pull
There are two kinds of force.
contact force
If the objects must be in contact with each other
field force
If the objects don’t need to touch to push or pull each other, it is a
Is magnetism a field of contact force?
What device can you use to detect a magnetic field?
a compass

14. Magnetic Fields
Model train

15. Magnetic Fields
Magnetic field lines can be used to represent the magnetic fields.
The field gets weaker with distance from the magnet. Field lines close to each other indicate a strong field while field lines farther apart indicate a weaker field.

16. Earth’s Magnetic Field

17. Earth’s Magnetic Field
Imagine that there is a big bar magnet inside the Earth, what would that look like?

18. Magnetic North and South
The Earth’s magnetic poles – note that they are not in same place as the Earth’s geographic poles.

19. Magnetic North and South

20. The Solar Wind
The solar wind streams off of the Sun in all directions at speeds of about 400 km/s (about 1 million miles per hour).
This wind leads to a mass loss of more than 1 million tons of material per second.
It is basically an ionized gas, mainly composed of protons and electrons

21. comet Tempel 1

23. Earth’s magnetic field is essential for life, it protects us from solar winds

26. Compasses
One way to analyze a magnetic field’s direction is to use a compass.
A compass is a magnet suspended on top of a pivot so that that magnet can rotate freely. The compass aligns with the Earth’s
magnetic field.
A compass can be used for navigation
because the Earth’s magnetic field
acts like a giant bar magnet.

27. Electromagnetism
Magnetism and electricity are related

28. Faraday's law of induction
Electromagnetic induction was discovered in 1831 by Michael Faraday
He made a coil by wrapping a
paper cylinder with wire
and then moved a magnet
back and forth inside the
cylinder.
He was able to generate
current in the wire

29. Faraday's law of induction
Electromagnetic induction is the production of a potential difference (voltage) across a conductor when it is exposed to a varying magnetic field.

30. Faraday's law of induction
Electromagnetic induction

31. Faraday's law of induction
Instead of moving the magnet near a wire, looped wire can be moved in a magnetic field.

32. Faraday's law of induction
There are two key devices that have been produced using Faraday’s work
Electric motor: converts electricity into mechanical energy by stimulating the coiled wire to move in a magnetic field with electric current
Generator: is simply the same process in reverse, converting mechanical energy into electricity. Almost all of the electrical energy we use in our daily lives is supplied by electric generators.

33. Faraday's law of induction

34. Video (with quiz)
Click here
17 minute video