# Magnets by ewghwehws

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```									Magnets

Jiacheng Xu
Tao Chen
Chu Wu
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
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)
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.
lodestone VS electromagnets

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

• Maglev trains
• Sort magnetic and non-magnetic materials
• Magnets are also used in compasses
What you need
• card stock or any other heavy
paper

• magnetic tape

• markers or crayons
(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.
Reference
http://www.coolmagnetman.com/magreview.htm
http://www.squiglysplayhouse.com/ArtsAndCrafts/Crafts/Magnets.html
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