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Chapter 3 Magnetism

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Title: Chapter 3 Magnetism


1
Chapter 3 Magnetism
  • The last EM chapter

2
Magnets
  • Attract certain other materials
  • Iron, Nickel, Cobalt, Steel
  • Obvious
  • Refrigerator
  • Not Obvious
  • Blender, Microwave, doorbell

3
Magnetism
  • Force exerted on a magnet
  • Can act at a distance
  • Can push or pull

4
Maglev Train
  • -300 mph
  • -Does not touch
  • track

5
Magnetic Poles
  • Where the magnet is the strongest
  • Bar magnet
  • N S poles
  • Magnet will align with the poles of the earth if
    suspended
  • If you break it in half you will get 2 smaller
    magnets with a N S Pole
  • Horseshoe bent bar magnet
  • Like electricity opposites attract

6
Magnetic Fields
  • A region around a magnet that exerts a force
  • If a piece of iron is in the field it will be
    drawn towards the magnet
  • Lines always go from pole to pole

7
Fields multiple magnets
8
Magnetic Materials
  • Natural
  • Lodestone
  • First discovered in Magnesia Greece
  • Man Made
  • Bar, Round, Horseshoe
  • Materials attracted to magnet
  • Iron, Nickel, cobalt
  • Materials not attracted
  • Wood, Aluminum, Galvanized Steel

9
All atoms have a magnetic field
  • Arrangement of the magnetic field of the atoms
    determines if it is magnetic

10
Nonmagnetic materials
  • The magnetic fields of the spinning electrons
    point in different directions cancelling each
    other out

11
Magnetic Materials
  • Have magnetic domains (groups of aligned fields),
    but point in different directions

12
Magnets
  • When a material is magnetized the fields of all
    the domains point in the same direction

13
Temporary Permanent Magnets
  • When a paper clip sticks to a magnet, the paper
    clip itself becomes a magnet.
  • Permanent Placing magnetic materials in a
    strong magnetic field
  • Can be made weak knocking the domains out of
    alignment
  • Dropping it
  • Exposing to high temperatures

14
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15
Compasses
  • Compass
  • a magnet that can spin freely
  • Always points towards magnetic north
  • First made of loadstone

16
Earth as a magnet
  • Earth acts as if a huge bar magnet was inside of
    it
  • Magnetic field caused by the iron and nickel core

17
a
  • a

18
Earths Magnetic Field
  • Affects everything that is magnetic
  • Most metals (cans in your cupboard)
  • 2 north poles
  • True north 90 North
  • Magnetic north where the compass will point
  • Some think the poles can reverse themselves
  • Evidence Rocks with iron on the ocean floor line
    up with the direction of the pole.

19
Magnetism The Atmosphere
  • Suns radiation can be damaging to living things
    but the magnetic field protects us
  • Many of the particles are deflected towards the
    poles
  • Northern lights

20
a
  • a

21
3.2 Current Magnetism
  • Discovered by accident
  • Electricity passed through a wire moved a compass
    needle
  • Current creates a magnetic field

22
Electromagnetism
  • Magnetism that results from an electric current
  • Moving electrons produces a magnetic field
  • More current stronger magnetic field

23
Increasing strength
  • Passing current through a coiled wire increases
    magnetic field
  • Which side is the north pole depends on the
    direction the current is flowing

24
Electromagnets
  • Wrapping wire around a piece of steel or iron.
  • Magnetic field disappears when the current is
    turned off

25
Electromagnet Use
  • Junk Yards

26
Use of Electromagnets
  • Computers store information on a hard drive with
    billions of magnets
  • VHS Tapes
  • Credit cards

27
Motors Electric Magnets
  • Convert energy of an electric current into motion

28
Motors
29
How it works
  • 1st

30
2nd
31
3rd
32
Uses of Motors
  • Power Windows
  • SEPTA Trains
  • Wristwatch needle
  • CD Player

33
3.3 Generators
  • Converts energy of motion to electric current
  • Essentially a motor in reverse
  • Turned manually

34
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35
Types of Current
  • Direct Current (DC) Electric charge flows in one
    direction
  • Batteries
  • Alternating Current (AC) Electric charge
    alternates direction
  • House current

36
Electronics
  • Most items run on either AC, or DC
  • Some run on DC only and need to convert the
    current from AC to DC

37
Magnets Voltage
  • Used to control voltage
  • Wire is coiled around an iron ring with one side
    with more loops.
  • Changes the voltage by creating an electromagnet

38
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39
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40
3.4 Generators
  • Water from rivers Lakes
  • Steam

41
Watts and Kilowatts
  • Watt (W) the rate at which energy is used by an
    appliance
  • Measured using a formula
  • Electric Power voltage x current
  • PVI
  • Kilowatt 1000 watts

42
Appliances
  • DVD player 20 W
  • Electric blanket 70 W
  • Television 110 W
  • Refrigerator 700 W
  • Microwave 1000 W or 1KW
  • Clothes Dryer 3000W or 3KW

43
Your Electric Bill
  • Based on how much you use, and how long you use
    it
  • Energy Used Power x Time
  • EPt
  • Measured in Kilowatt Hours
  • Running a 3KW appliance for 2 hours uses 6KWH

44
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45
  • FIN
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