around the nucleus of an atom. This is
called an electromagnet.
Small, thin pieces of iron are
attracted to a red bar magnet.
The pieces of iron line up to
show the magnetic field of the
magnet.
In the photo,
the magnetic
field is strong
where the
pieces of iron
are close
together. The
field is weak
where the
pieces are far
apart.
18 Magnet and Magnetism BRITANNICA STUDENT ENCYCLOPEDIA
Hard and Soft Magnets
Because of the way their electrons are
arranged, the metals iron, steel, nickel,
and cobalt make good magnets. Once
these metals become magnets, they can
stay magnets forever. Then they are
called hard, or permanent, magnets. But
these metals and others can also act like
magnets only sometimes, after they have
been near a hard magnet. Then they are
called soft, or temporary, magnets. Most
other materials—for example, water, air,
and wood—have very weak magnetic
properties.
Properties of Magnets
Magnets strongly attract objects that
contain iron, steel, nickel, or cobalt.
Magnets also attract or repel (push
away) other hard magnets. This happens
because every magnet has two opposite
poles, or ends: a north pole and a south
pole. North poles attract the south poles
of other magnets, but they repel other
north poles. Likewise, south poles
attract north poles, but they repel other
south poles.
The magnetic forces between the two
poles of a magnet create a magnetic field.
This is the area affected by the magnet. A
magnetic field surrounds all magnets.
Uses
One of the earliest uses of magnets was
in compasses. A compass is a needleshaped
magnet that is free to turn
around. The planet Earth is a giant magnet.
Because the south pole of a compass
is attracted to the north pole of Earth,
the compass needle always points north.
Today magnets are found in many places.
Magnets hold papers on refrigerator
doors. They also hold the doors shut.
Credit cards have a magnetic strip.
Automatic doors, stereo speakers, and
many electric motors use electromagnets.
#More to explore
Compass • Electricity • Iron • Metal
Magnolia
Magnolias are trees and shrubs. They are
known for their large flowers. People
plant magnolias in parks and gardens.
Some magnolia wood is used to make
furniture.
There are about 80 species, or types, of
magnolia. They grow in North America,
Central America, and Asia.
Many magnolias are about 40 to 80 feet
(12 to 24 meters) tall. They usually have
smooth, gray bark. Their leaves are large
Bar magnets can show how unlike poles
attract each other and like poles repel each
other.
If a bar
magnet is cut
in half, each
half becomes
a complete
magnet with a
north pole and
a south pole.
BRITANNICA STUDENT ENCYCLOPEDIA Magnolia 19
and oval. Some magnolias are evergreen.
This means that they keep their leaves
year-round.Others are deciduous. They
lose their leaves in winter.
The flowers of a magnolia are white,
yellow, pink, or purple. They can be 10
inches (25 centimeters) or more across.
Most magnolia flowers have 6 to 12 large
petals. They usually bloom in the spring
and early summer. Some flowers have a
beautiful smell. After flowering,
magnolias produce a fruit shaped like a
cone. Inside are reddish seeds. The fruit
splits open in the fall. When this happens,
the seeds hang down by thin threads.
Many types of magnolia are popular.
The southern magnolia has large, white
flowers that smell like lemons. The bigleaf
magnolia grows up to 50 feet (15
meters) high. Leaves of the umbrella tree
are 2 feet (61 centimeters) long. The
cucumber tree is named after its fruits,
which are shaped like cucumbers.
#More to explore
Flower
Magpie
Magpies are bold, noisy birds that have
many calls. They belong to a group of
birds called songbirds. However, their
voices are rather harsh sounding. Like
their relatives the crows, magpies are
known for their intelligence. For
instance, magpies hide objects and then
remember where to find them again.
People often keep these birds as pets.
Magpies are in the same scientific family
as crows, ravens, and jays. There are
several different species, or types, of
magpie. Common types include the
Eurasian magpie and the black-billed
magpie.
Magpies live in Europe, Asia, Africa, and
North America. These birds build nests
in tall trees. However, they need open
grasslands nearby for feeding. Thus they
are often found at the edges of forests.
Magnolias are known for their large, beautiful
flowers.
Magpies are intelligent, noisy birds.
20 Magpie BRITANNICA STUDENT ENCYCLOPEDIA
Eurasian and black-billed magpies are
about 18 inches (46 centimeters) long.
They are mostly black except for their
white bellies and white patches on their
wings. They have long black tails. In
sunlight their wings and tails look shiny
blue or green. Several types of magpie
found mainly in Asia have bright blue or
green feathers.
Magpies eat many different kinds of
food. They eat insects, dead animals,
fruit, seeds, and even the eggs and chicks
of other birds. When magpies have too
much to eat all at once, they stash food
away to eat later.
Magpies have a place in European folklore.
Some people think of them as
thieves. Others think they bring bad
luck.
#More to explore
