Elenco Snaptricity&reg - Manual (Page 53)

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Compass Project #43
Educational Corner:
All materials have tiny particles with
electric charges, but these are so well
balanced that you do not notice them
unless an outside voltage disturbs
them. The same tiny particles also
have magnetic charges, which are
usually so well balanced that you do
not notice them unless a magnetic field
disturbs them.
Magnets are materials that concentrate
their magnetic charges at opposite
ends. One side attracts while the other
repels, but the overall material is
neutral. Most magnets are made of
iron. The name “magnet” comes from
magnetite, an iron ore that magnetism
was first seen in.
The earth we live on is a giant magnet,
due to its iron core. A compass needle
always points north because it is
attracted to the earth’s magnetic field.
The opposite ends of a magnet are
often labeled north and south,
representing the north and south poles
of the earth. For centuries ships have
used suspended magnets for
navigation.
1 3
2 4
1. Hold your compass away from everything, notice that the red
arrow always points north. Spin it around, the red arrow will
adjust and resume pointing north.
2. Now place the compass next to a large iron object, such as a
refrigerator or car. If the object is heavy enough, the red arrow
will point toward it.
3. Now place your magnet near the compass. The red arrow will
immediately point toward the black “S” side of the magnet,
ignoring a nearby refrigerator.
4. Pull out a 2-snap wire, a paper clip, the electrodes, the iron
core rod, and the thin bar. Decide which of these you think the
magnet will pick up, then try it and see if you were right. Do
the same for other materials in your home.
Operation
1. The earth’s core is made of iron, which has a magnetic field.
The compass points north because it is attracted to this
magnetic field. This allows compasses to be used for navigation.
2. Large iron objects also exert a small magnetic field, which may
attract a nearby compass. The magnetic field is much weaker
than the earth’s, but much closer to the compass.
3. Magnets have been induced to have a concentrated magnetic
field at either end. This magnetic field is much stronger than
ordinary iron objects that may be nearby.
4. The physical properties of iron make it easy to induce a
magnetic attraction in. This doesn’t work for other metals or
other materials.
Description
Snappy says: a compass
actually points to the earth’s
magnetic north pole (which is in
the Arctic Ocean just north of
Canada), not the geographic
north pole.
Refrigerator
Door