Download Introduction to Magnetism - Appoquinimink High School

Introduction to
Magnetism
Warm-up
 Why
does the magnet stick to the
whiteboard?
History of Magnetism
 The
term magnetism stems from a rocks
found in the region of Magnesia, Greece
called lodestones.
 In the 1100’s, the Chinese used magnets
to help navigate their ships and created
the first compasses.
 In the 1700’s Charles Coulomb studied the
forces between lodestones.
Hans Christian Oersted
 In
1819, Danish scientist discovered the
relationship between electric currents and
magnetism.
 This lead to a world-wide search for the
links between electricity and magnetism.
 We will be discussing all of these links
later this week
Magnetic Poles
 Why
do magnets repel if they are oriented
one way, but attract if they are oriented
another way?
Magnetic Poles
 Magnets
have two poles, North and South.
 The magnetic fields are strongest at the
North and South poles, and weaker the
farther you get away from them.
 What
happens if you break a magnet? Is
it possible to isolate a pole?
 Using
a compass, let us find which pole is
which on each magnet.
 What
happens when we put a North Pole
near a South pole?
 What
happens when we put a South Pole
near a North Pole?
How does a Compass Work?
 If
a compass is held on a table, without
anything near it, how come the needle
points in a specific direction?
Earth’s Magnetic Poles
 The
Earth has a magnetic field, so
therefore, a compass with a needle that is
attracted to magnetic poles (like a paper
clip) points towards the poles.
 Ready
for the confusing part… the
geographic North Pole is actually the
magnetic South Pole… and it isn’t located
directly North
 The
magnetic South pole, is located just
North of the Hudson Bay in Canada.
 That
is 1500km away from the Earth’s
Geographic North Pole.
 earth's magnetic field
Why is the Earth Magnetic?
 Although
the Earth has large deposits of
iron ore beneath its surface (a magnetic
substance), the high temperatures prevent
the iron from retaining magnetism.
 It is predicted that the magnetic field is due
to the movement of convection currents at
the Earth’s core.
Are other planets magnetic?
 There
is evidence that the rate of rotation
is related to the strength of a planet’s
magnetic field.
 For example, Jupiter rotates faster than
Earth and has a stronger magnetic field.
How are some rocks magnetic and
some not?
 Iron
ore achieves magnetism because it is
subjected to the Earth’s magnetic field
over long periods of time.
 Observe
what happens to the paper clip
as it is attached to a permanent magnet
for a long period of time.
Magnetic Field lines
 Just
like electric fields, magnetic fields can
be shown through field lines.
 Predict
what the field lines would look like
for the following magnet: