Magnets

1
Magnets

• Jiacheng Xu
• Tao Chen
• Chu Wu

2
What we learn in class

• Recall that a magnet is a material or object that
  produces a magnetic field.
• Our Professor mentioned a little about magnets.
  Now, we will continue to learn more about Magnets

3
What are Magnets

• Magnets are materials that produce a magnetic
  field of their own. Extreme examples of magnets
  are (1) "hard" or "permanent" magnets (like
  refrigerator magnets), which remember how they
  have been magnetized, and (2) "soft" or
  "impermanent" magnets (like the material of a
  refrigerator door)

4
Two types of Magnets

• lodestone
• natural permanent magnet
• exert a force on objects without any outside
  influence
• electromagnets
• They are made by surrounding certain materials
  with a coil of wire.
• When an electric current is passed through the
  coil, these materials exert a magnetic force.

5
lodestone VS electromagnets
lodestone
6
How do Magnets work

• The molecules in magnets are arranged so
  that the electrons spin in the same direction.
  This arrangement of atoms creates two poles in a
  magnet, a North-seeking pole and a South-seeking
  pole.

The magnetic force in a magnet flows from the
North pole to the South pole. This creates a
magnetic field around a magnet.
7
How do Magnets work

• If you try to push the South poles or north
  poles together, they will repel each other.

• If you try to push the south pole and north pole
  together, they will attract each other.

8
Temperatures and Magnets

• The maximum temperature that a magnet may
  be effectively used at depends greatly on the
  'permeance coefficient' - which is a function of
  the magnetic circuit - the magnet is operating
  in. The higher the permeance coefficient (the
  more 'closed' the circuit), the higher
  temperature at which the magnet may operate at,
  without becoming severely demagnetized. Shown
  here are approximate maximum operating
  temperatures for the various classes of magnet
  material. At temperatures close to those listed
  here, special attention may be needed in order to
  ensure that the magnet will not become
  demagnetized.

9
Temperatures and Magnets
10
The use of Magnets

• Maglev trains
• Sort magnetic and non-magnetic materials
• Magnets are also used in compasses

11
Make your own Magnets

• What you need
• card stock or any other heavy paper
• magnetic tape
• markers or crayons

12
Make your own Magnets (Cont.)

• What you do
• Cut a little piece of any shapes from the card
  stock and color it with markers or crayons.
• Place a small piece of magnetic tape onto the
  back of the magnet. Make sure to remove the
  backing!
• Use the magnets to stick paper or sheets on your
  fridge or any other metal surface.

13
Reference

• http//www.coolmagnetman.com/magreview.htm
• http//www.squiglysplayhouse.com/ArtsAndCrafts/Cra
  fts/Magnets.html
• http//images.google.com/imgres?imgurlhttp//www.
  launchpnt.com/fileadmin/maglev/CloseUp_01_web.jpg
  imgrefurlhttp//www.launchpnt.com/Maglev_PRT.480.
  0.htmlh169w300sz16hlenstart37tbnidNW62
  MzoSfeLFrMtbnh65tbnw116prev
• http//images.google.com/imgres?imgurlhttp//www.
  uscg.mil/diversity/COMPASS/Compass_pin.JPGimgrefu
  rlhttp//www.uscg.mil/diversity/COMPASS/h461w
  512sz33hlenstart3tbnidWqjdvRPo-7VuSMtbnh
  118tbnw131prev
•  http//images.google.com/imgres?imgurlhttp//www
  .materialflow.com/MFG-PRODS/Aigner-Index/Magetic-R
  oll-Stock.jpgimgrefurlhttp//www.materialflow.co
  m/Label-Holders-Magnetic.htmh299w313sz10hl
  enstart36tbnidtCkey6EMWWJTjMtbnh112tbnw11
  7prev
•  http//images.google.com/images?qMagnetsgbv2n
  dsp18svnum10hlenstart54saN
• http//en.wikipedia.org/wiki/Magnets
•  http//www.eia.doe.gov/kids/energyfacts/sources/e
  lectricity.html
•  http//www.magnetsales.com/index.htm

14
Thank you
Jiacheng Xu Tao Chen Chu Wu