Download Magnetism - Howard Elementary School

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Chapter 36 Summary – Magnetism
There are 2 main ways that magnets are similar to electric charges: like charges
repel and opposites attract, and the force between is inversely proportional to the
distance between them. This means that closer is stronger, and further is weaker.
Electric charges are positive or negative, magnetic poles are north or south. One main
difference is that magnetic poles cannot be isolated. The area around magnets that are
affected by the magnetic forces is called a magnetic field. We cannot see this area but
we can represent it with magnetic field lines. These lines travel in loops from north to
south on the outside of a magnet and south to north on the inside. Closer field lines
mean stronger forces, further mean weaker. The strongest areas are near the poles. If a
compass is brought near a magnet, it will align parallel with the magnetic field lines.
Magnetic fields are produced by the motion of electric charges. The motion more
specifically is orbiting or spinning electrons. Each spinning electron creates a tiny
magnet and most magnetic forces come from spinning electrons. Clusters of electrons
spinning and pulling together are called magnetic domains. In most materials, those
domains pull in many random directions and cancel each other out so the material is not
magnetic. In some materials, iron is a good example, those domains can easily be made
to organize. All those tiny forces working together make the whole object a magnet.
When some materials are brought near a permanent magnet, their domains will align and
they will be made into a temporary magnet. An electric current produces a magnetic
field. A current carrying wire will have a magnetic field around it. If a current carrying
wire is made into a loop, the field gets concentrated and the forces are made stronger. A
current carrying wire wrapped around a potentially magnetic material is an
electromagnet. All you need to make an electromagnet is a battery and wire coiled
around a potentially magnetic material.