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MAGNETISM
Teacher: Lourdes Valencia Bergaz
Subject: Science
Students: Primary year 6
School: CEIP “Narciso Alonso Cortés” Valladolid
THE EXPERIMENTAL METHOD
Previous knowledge:
What is a force?
What effects do forces produce on objects?
Form hypotheses:
What type of forces do you know about?
By making predictions.
Do you know what a magnet is?
Design and conduct the
EXPERIMENTS
Analyze the results of
the experiments
Draw a conclusion
We are going to study one of the most amazing forces:
MAGNETISM
A bite of History
Pliny The Elder (23-79 AD, Roman) wrote this legend about the beginning of magnetism:
Once upon a
time, there was a
shepherd called
Magnes who lived
in Magnesia, a
region in Greece.
One day, Magnes
was herding his
sheep and he felt
tired. He sat down
on a black
rock and when he
wanted to stand up
he almost couldn’t,
because the
nails of his shoes
and the metal tip of
his staff had stuck to
the rock.
Source: “Magnetismo en el Aula”
Lodestone/Magnetite
This rock is lodestone
or magnetite, the only
natural magnet found
in nature. And this
phenomenon is called
magnetism.
The children are looking at
the pieces of magnetite.
COMICS ABOUT THE STORY OF MAGNES
INVESTIGATING MATERIALS USING MAGNETS
We are going to check which materials are magnetics:
Choose different materials from these boxes.
Do worksheet: ‘Magnetic Materials’
Don’t forget to make your prediction before starting the experiment with magnets.
The
children
are trying
different
materials
Worksheet they
have done
Analyze the results of the experiment
All the
magnetic
materials are
metals.
Only some
metals were
attracted by
magnets.
The metals attracted by
magnets were iron,
steel and nickel.
Conclusion: IRON, STEEL AND NICKEL ARE MAGNETIC MATERIALS
Finding out some facts about magnetism.
Put one end of the iron nail by the
magnet. What happens if we place a
paper clip at the other end of the nail?
It sticks to the
nail
Take the nail away from the magnet. Now, place the
paper clip by the nail. Is the paper clip attracted by the nail?
Does this mean that the nail is a magnet too?
Conclusions: The magnet and the nail together behave as
a longer magnet.
The nail becomes a temporary magnet. This effect is
called induced magnetism.
Is the nail attracted by the magnet only when they are together?
How can we check this?
What objects?
We can place
different objects
between the nail
and the magnet.
A piece of
cardboard
A piece
of cork
A piece of
paper
A thick plastic
tray
Let’s do it.
Try with other objects.
Conclusion: When we place an object between the magnet and the nail, depending
on the thickness of the object, the magnet attracts the nail or not.
Comparing the force of different magnets
Make your own magnet: Stroke a
steel object with a bar magnet
about fifty times. Move the Magnet
in one direction only, and raise it at
the end of each stroke.
Compare the force of the magnet and the force of your magnet.
Instructions:
- Put a ruler on the table.
- Place a pin at zero on the ruler.
- Put the magnet at 10 cm. Push
the magnet slowly towards the pin.
- When the pin jumps to the
magnet, look at the number beside
the magnet.
- Write down the distance in the
table below.
- Repeat all the steps with your
magnet and other magnets.
Analyze the results of the experiment
Not all the
magnets
have the
same force.
There are
strong
magnets and
weak ones.
The distance is important.
If the pin is far away from
the magnet, it is not
attracted by the magnet.
Conclusion: There is a space where the force
of the magnet works. This space is called its
magnetic field. Each magnet has a different
magnetic field.
Magnetic field
Try to place two magnets together. Place them in different positions.
Analyze the results of the experiment
If we put a
magnet next to
another one they
were attracted.
But when we
change the end
of one of the
magnets they
were repelled.
Conclusion: Magnets have
two different ends. They are
called poles. North and
south pole
A bite of History
The earliest discovery of the properties of lodestone was by the Chinese.
They found out that a lodestone would always point in a north-south
direction if it was allowed to rotate freely. The Chinese developed the
mariner's compass more than 4000 years ago. The earliest mariner's
compass consists of a spoon-shaped magnetite object with a smooth
bottom, set on a polished copper surface. When pushed it rotated freely
and usually came to rest with the handle pointing South.
At the beginning, chinese people
used the spoon compass with a
magic purpose.
They called it ‘The Magic Spoon’.
Source: “Magnetismo en el Aula”
Let’s make a Chinese compass.
We will need: a spoon
a bar magnet
a glass plate
Let the spoon rotate freely
and when it stops, observe
where the handle of the
spoon points.
Let’s see what happens if we turn the magnet round in the Chinese
compass.
The handle of the
spoon points to
the opposite
side.
A bite of History
It’s time to talk about Alexander Neckam.
He was an English teacher who was interested
in the study of natural history.
Alexander Neckam (1157-1217) was born in
St Albans, Hertfordshire (England) on 8th
September, 1157, on the same night as King
Richard I. Neckam's mother nursed the prince
with her own son, who thus became Richard's
fosterbrother.
He went to Paris. In 1180, he became a teacher at the
university. It was probably in Paris that Neckam heard how
a ship, along with its other stores, must have a needle
placed above a magnet, which would rotate until its point
faced North, and guide sailors in bad weather or on starless
nights.
This device was the first floating compass.
Design your own compass. Here you have same examples.
Source: “Magnetismo en el Aula”
The children are designing and making their own compasses
Some of the compasses the
children have made.
Leave them to rotate freely. What happens when they stop moving?
All of them are
parallel and
pointing to the
same direction.
Let’s check the direction by looking at a
real compass. What can you see?
The north pole of the
magnet in the compasses
points to the North; and the
south pole of the
compasses points to the
South.
Why do all the compasses orientate in the same north-south direction?
Because the Earth is like a
very big magnet, and it has its
own magnetic field.
Act as a compass: look at the
compass and face North. Your back
points South. Stretch your arms.
Your right arm points East and your
left arm points West.
Now we know where the north
pole is in our magnet. Make a red
cross on the north pole of your
magnet.
Let´s work with two magnets again.
Which poles attract each other?
Which poles repel each other?
Analyze the results of the experiment
Two magnets with
unlike poles
facing attract
each other.
Two magnets with
like poles facing
repel each other.
The north pole of the
compass points to the
North Pole of the Earth
because it is attracted by
the south magnetic pole of
the Earth.
Conclusion: The Earth behaves like a gigant magnet. It has a
north and south magnetic pole. The north magnetic pole is
located in the south geographic pole of the Earth, and the south
magnetic pole is located in the north geographic pole of the Earth.
A bite of History
The first attempt to separate fact from
superstition came in 1269 when a French
soldier named Peter Peregrinus wrote a
letter describing everything that was known,
at that time, about magnetite.
It is said that he did this while standing guard
outside the walls of Lucera which was under
siege. While people were starving to death
inside the walls, Peter Peregrinus was
outside writing one of the first 'scientific'
reports and one that was to have a vast
impact on the world.
Source: “Magnetismo en el Aula”
He was one of the few medieval scientists to have conducted experimental
methods.
Let’s do some of his experiments.
A model of the Earth
You will need: a plasticine ball
a bar magnet
some iron filings
Sprinkle some iron filings on your
model of the Earth.
What have we checked?
The poles of the Earth
have a strong force of
attraction.
Lines of force in a magnetic field
Follow the instructions and do worksheet ‘Fields of force’
a) Put a bar magnet under a sheet of
paper.
b) Sprinkle some iron filings over the
paper.
c) Tap the paper gently. The iron filings
are attracted to the magnet and form a
pattern. This pattern shows what the
magnetic fields looks like.
Pictures they have drawn
of the lines of force.
You can also draw the lines of force by using a compass.
a) Place a bar magnet on a sheet of paper and slowly
drag the compass around the magnet.
b) Draw arrows in the same direction that the compass
points to.
Analyze the results of the experiment
The lines go from
one pole to the
other
The iron filings
draw a pattern of
lines.
In what direction?
From the north
pole to the
south
Conclusion: The lines of force go
away from the north pole of a magnet
and towards its south pole.
So The Earth behaves as a
magnet, we can draw the lines of
force in the Earth’s magnetic field
as in this picture.
Can we separate the poles of a magnet?
Let’s try. Follow these instructions:
a) Unfold a steel paper clip, you will have a piece of
steel wire.
a) Magnetize it.
b) Ask your teacher to cut the wire into small pieces with
pliers.
Place different pieces of wire together.
What have you noticed?
Each small piece
of wire is like a
complete magnet.
Source: “Magnetismo en el Aula”
Analyze the results of the experiment
It’s imposible to
separate the
north and the
south pole of a
magnet
All small pieces of
wire have a north
and a south pole
How can you
explain this?
Because a magnet
works as if it has
little magnets inside
it.
Conclusion: All magnets have a north and a south pole,
because they are made of tiny magnets called magnetic
domains with both poles.
Is it posible to change the polarity of a magnet?
Let’s try.
a) Magnetize a needle.
b) Hang the needle from a string and leave it
to rotate freely.
c) When it stops, check with a compass
where the north pole is.
d) Put a strong magnet by the needle, and
leave it to rotate freely.
e) When it stops, check again where the north
pole is.
Worksheets they have done: ‘Record experiment worksheet’
Analyze the results of the experiment
But when we put
the strong magnet
by the needle, the
tip points south.
At the beginning, the
tip of the needle
points north
The poles of the
needle have swaped
Conclusion: Weak magnets can reverse their polarity by the action of a
strong magnetic field.
Facts we have discovered about magnetism:
1.- Magnetism is a force of attraction between magnets
and magnetic materials and it works at a distance.
2.- Magnets attract only some materials called magnetic ones.
3.- Magnetic materials become a magnet when they are
next to it, this effect is called induced magnetism.
4.- The force of a magnet can pass through thin objects
such as paper, cardboard or plastic.
5.- Every magnet has a magnetic field around it.
6.- Every magnet has two poles, a north and south pole.
7.- Unlike poles attract each other and like poles repel
each other.
8.- The Earth is a huge magnet. It has two magnetic poles
and it is surrounded by a magnetic field.
9.- The Earth’s magnetic field is what causes the needle of a
compass to point either north or south.
10.- The magnetic field is made up of lines of force running
from the north pole to the south pole of the magnet.
11.- It’s imposible to separate the two poles of a magnet,
because magnets are made of very tiny magnets called
magnetic domains.
12.- Magnets with a weak force can reverse their polarity
thruogh the action of a strong magnetic field.
And next….
ELECTRICITY and
the relactionship between
ELECTRICITY and MAGNETISM