1. Magnetism(Review)

2. What do we know about magnets?
2 Magnetically opposite poles:
North Pole and South Pole
Like poles repel and Opposite poles attract
“We’ll get back to this later”

3. What types of things do magnets attract?
“Do magnets attract all metals?”
Magnets only attract objects made of iron, cobalt, or nickel!!
These metals are called the “Iron Triad”
See Periodic Table
You can also only make a magnet out of these 3 metals.
Those “rubber” magnets have iron, cobalt or nickel in them.

4. Magnetic Domains
The molecules of most substances have no orientation to them.
In a magnet, the molecules align themselves in a very specific pattern.

5. Magnetic Field Surrounding all magnets is a magnetic field.
Magnetic Field is the area surrounding a magnet where the magnetic force acts.
Magnetic Field Lines

6. The North Pole is the pole that the magnetic field lines move out of.
The South Pole is the pole that the magnetic field lines move into.

7. Magnetic Field Lines
Magnetic Field lines always move out of the North end and into the South end!!

8. Magnetic Field Lines of Interacting Magnets
Lines of Attraction
Lines of Repulsion

9. What happens if you break a bar magnet in half?
Mr. Eidson
You get 2 bar magnets both with a North and a South pole!!

10. Breaking a Bar Magnet

11. Is there a relationship between electricity and magnetism
Is there a relationship between electricity and magnetism? Let’s see what I discovered!!!
Hans Christian Oersted

12. Oersted’s Law
The flow of electricity through a wire conductor produces a magnetic field around the wire.

13. 2 things affect the strength of a magnetic field:
Amount of current
Increase current = increase strength
Decrease current = decrease strength
# of coils of wire
More turns of wire = more strength
Less turns of wire = less strength

14. If you take an iron core and insert it into a coil of current carrying wire, you have a temporary magnet called an electromagnet!!

15. Strength of an Electromagnet
2 things affect the strength of an electromagnet(same 2 things that affect the strength of a magnetic field):
Amount of Current
# of turns of wire(# of coils)

16. Uses of Electromagnets
Electric Meters: because of their ability to detect current(only work when there is one), electromagnets are used in a variety of electric meters.
Ammeter—measures current
Wired in series
Voltmeter—measures voltage
Wired in parallel
Galvonometer—”detects” current

17. Uses of electromagnets(cont.)
Motors
Use electromagnets to convert electrical energy into mechanical energy
An electromagnet turns inside a permanent magnet

18. Motors

19. Faraday and Henry discovered that moving a wire through a magnetic field, or moving a magnetic field through a coil of wire “induced” a current on the wire!!
Electromagnetic Induction—process in which moving a wire through a magnetic field produces a current on the wire.

20. ….produces a current on a wire. “Did we just “create” electricity”
Generators—use electromagnets to convert mechanical energy into electrical energy.

21. Generators

22. Are you talking about me?
Other Uses of electromagnets:
Transformers
Are you talking about me?
Not this Kind!!!!

23. Alternating vs. Direct Current
Alternating Current
Direct Current
Current alternates, one direction, then the other.
Current only goes in one direction.
Plug it in, Plug it in!!

24. Transformers
Used to increase or decrease the voltage of alternating currents.

25. Transformers Consist of 2 coils of wire.
Primary Coil
Alternating current enters
Secondary Coil
Alternating current leaves
It’s the difference in the number of turns of wire on each coil that causes the voltage the change.

26. 2 Types of Transformers Step-up Transformer Step-down Transformer
Increase voltage
Primary more turns than secondary
Step-down Transformer
Decrease voltage
Secondary more turns than primary

27. Math of a Transformer:

28. A step-up transformer has 400 turns on its primary coil and 600 turns on its secondary coil. If the primary coil is supplied with 120 V of alternating current, what will be the secondary (output) voltage?
ns= 600 turns
np= 400 turns
Vs= ?
Vp= 120

29. Example #2

31. Example #3

33. Independent Practice: