Download Electromagnetic Forces

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1. What is a magnet?
2. What is magnetism?
1. A magnet is any material that attracts
iron and materials that contain iron.
2. The attraction or repulsion of magnetic
materials
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Every magnet has two ends to it; north
pole and a south pole. These ends are called
a magnetic pole.
What happens when you hold two magnets
together?
If you bring the north pole side near the
south pole side, the two unlike poles
attract one another.
If you bring two norths, or two souths
together they repel each other.
 The area of magnetic force
around a magnet is known as
the magnetic field.
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Magnetic Field lines are lines that map out
the invisible magnetic field around a
magnet.
Spread out from one pole, curve around the
magnet and return to the other pole.
The lines never cross when they move from
the North pole to the South pole.
The closer together the lines are, the
stronger the fields.
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If you were to cover the magnet with
iron filings, they will form a pattern
similar to magnetic field lines.
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How does a compass relate to our lesson on
magnets?
A compass is a device that has a magnet on
a needle that spins freely.
It is used for navigation because its needle
points north.
Why does this happen?
Because Earth has a magnetic field around
it and two magnetic poles.
Earth’s core is a large sphere of metal
that occupies Earth’s center.
 Two parts to the core: inner & outer
parts
 The outer core is made of hot liquid
iron
 The motion of this iron creates a
magnetic field similar to the magnetic
field of a bar magnet.
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Scientist Hans Christian Oersted discovered
that the two were related by accident.
When he was holding a compass near the
wire, he observed that the compass needle
changed directions and created a current in
the wire
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To further his investigation, he set up several
compasses around a wire with no current and
noticed that all the needles pointed North.
Then, after he produced a current in the wire,
the compass needles pointed in different
directions to form a circle.
He then concluded that the current had
produced a magnetic field around the field.
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The relationship between electricity and
magnetism is called electromagnetism
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The magnetic field produced by a current has
a strength and a direction.
The field can be turned on or off, have its
direction reversed, or have its strength
changed
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To turn a magnetic field produced by a
current on or off, you just turn it on or off.
To change the direction of the magnetic field,
reverse the direction of the current
There are 2 ways to change the strength of
the magnetic field.
 1. Increase the amount of current in the wire
 2. Make a loop or coil in a wire
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What do trains, fans, microwave ovens, and
clocks all have in common?
All use electricity.
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We learned that magnetic forces can produce
motion. Example when magnets move away
or toward each other.
The ability to move an object over a distance
is called energy
The energy associated with electric currents
is called electrical energy.
The energy an object has due to its
movement or position is called mechanical
energy.
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When a wire with a current is placed in a
magnetic field, electrical energy is
transformed into mechanical energy.
This happens when the current causes the
wire to move