Download Comp Quest 22 SPI 0807.12.3

Comp Quest 22
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SPI : 0807.12.3
A compass points to the north because Earth itself is one giant magnet. In fact, Earth
behaves as if it has a bar magnet running through its center. The poles of this imaginary
magnet are located near Earth’s geographic poles. If you put a compass near a bar
magnet, the marked end of the needle points to the south pole of the magnet. Opposite
poles of magnets attract each other. The tip that points to the north is the needle’s
north pole. Therefore, the point of a compass needle is attracted to the south pole of
a magnet. A compass needle points north because the magnetic pole of Earth that
is closest to the geographic North Pole is a magnetic south pole. The compass needle
points to the north because its north pole is attracted to a very large magnetic south pole.
Although you can think of Earth as having a giant bar magnet through its center,
there isn’t really a magnet there. The temperature of Earth’s core is very high. The
atoms in it move too violently to stay lined up in domains. Scientists think that
Earth’s magnetic field is made by the movement of electric charges in the Earth’s
core. The Earth’s core is made mostly of iron and nickel. The inner core is solid
because it is under great pressure. The outer core is liquid because the pressure is
not as high. As Earth rotates, the liquid in the core flows. Charged particles move,
which makes a magnetic field.
The strength of a magnetic field decreases rapidly with distance from the magnet.
On the surface of the planet, Earth’s magnetic field is not very strong compared to
that of a nearby electromagnet, or even that of a permanent bar magnet. Even so, it
is very important. The magnetic field prevents charged particles from the sun, which
could harm living things, from reaching the surface.
1. Where is the south pole of Earth’s magnetic field?
A at the geographic south pole
B near the geographic south pole
C at the geographic north pole
D near the geographic north pole
2. Most of the charged particles in the solar wind are deflected before they
reach Earth’s surface. What causes this deflection?
A an electric field
B a magnetic field
C Earth’s gravity
D all of the above
Comp Quest 22
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3. What is the source of Earth’s magnetic field, according to current
theories?
F a large bar magnet
G alignment of the magnetic domains of the inner core
H moving metal ions in the outer core
J magnetic domains in the lithosphere
4. Why is a small bar magnet able to deflect a compass from Earth’s large
magnetic field?
A The bar magnet is much closer to the compass than the source of
Earth’s field.
B The bar magnet is made of magnetic material, and Earth is not.
C Solar wind absorbs Earth’s magnetic field.
D The lithosphere shields the compass from Earth’s magnetic field.
4. a. The moon has a completely solid core. Based on current theories about Earth’s magnetic field, why
would the moon not have a magnetic field?_____________________________________________________
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b. What could cause Earth’s magnetic field to reverse directions?___________________________________
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