Magnetism Magnets and Magnetic Fields

1
MagnetismMagnets and Magnetic Fields

• Physics
• Chapter 21 Section 1
• Pages 766-769

2
I. Magnets

• A. Magnets have two poles (ends)
• 1. North pole
• 2. South pole
• ? A magnet will attempt to line itself up with
  the magnetic field of the Earth

3
I. Magnets

• B. Technological applications of magnetism
• 1. Large electromagnets used to pick up heavy
  loads
• 2. Magnets used in meters, motors, loudspeakers
• 3. Magnetic tapes used in audio and video
  recording, and computer disks
• 4. Regulation of controlled nuclear fusion
  research
• 5. Maglev trains

4
I. Magnets

• C. Magnetic forces exist between magnets
• 1. Like poles repel (south-south, or north-north)
• 2. Opposite poles attract (south-north)

5
I. Magnets

• D. Magnetic poles always occur in pairs
• 1. Magnetic poles can never be isolated
• 2. If you break a magnet, each piece will have a
  north and a south pole

6
I. Magnets

• E. Permanent magnets
• 1. Unmagnetized iron can be magnetized by placing
  it near a strong permanent magnet or stroking it
  with a magnet
• 2. Process is reversible with heat
• or hammering

7
I. Magnets
8
I. Magnets
9
I. Magnets

• 3. Magnetic material is classified by how it
  retains its magnetism
• a. Soft easy magnetized, but easily lose
• the magnetism
• b. Hard not easily magnetized, but once
• magnetized retain magnetism

10
II. Magnetic fields
11
II. Magnetic fields

• ? A region in which a magnetic force can be
  detected
• A. Direction of a magnetic field is the direction
  in which the north pole of a compass needle
  points at that location (Figure 21-2, page 767)
• ? Magnitude of the field is higher closer to the
  pole

12
II. Magnetic fields
13
II. Magnetic fields

• B. To indicate
• 1. In the plane of the page ?
• 2. Into the page X
• 3. Out of the page

14
II. Magnetic fields

• C. North-seeking vs. South seeking
• 1. Bar magnets will seek or point to the
  Geographic north or south pole.
• 2. Geographic north magnetic south
• 3. Geographic south magnetic north

15
II. Magnetic fields
16
II. Magnetic fields

• D. True North vs. Magnetic North
• ? Magnetic declination difference between
  compass pointing at magnetic north and true /
  geographic north

17
II. Magnetic fields

• E. Earths field is like a bar magnet buried in
  the Earth
• ? Convection current in Earths liquid iron
  outer core are the source of the field
• ? Related to planet rotation.

18
(No Transcript)