Download What are Electromagnets

What are Electromagnets?
A wire carrying current, like a magnet, has a
magnetic field around it. Why? It just does, it’s a
law of physics. However, when the wire is curved
around a object, the magnetic field is a lot
stronger, than just a straight wire. Curving wire
around an object is called a “coil”. And, the more
coils around the object, the stronger the magnet
becomes.
Another was to increase the strength of the electro
magnet is to increase the current. (ie: by using a
stronger battery)
Of course this type of magnet is only temporary because when you
remove the current, the magnetic field no longer exists. In this
example, we call the iron nail the “core” of the electromagnet.
Electro magnets are used a lot in industry. They can be found in
computers, radios, telephones and many other devices.
Electromagnets are used a lot in heavy industry because they can
pick up very heavy objects, and then drop them when the current is
switched off.
QUESTIONS:
1. What is an electromagnet?
2. Why are these magnets called
temporary magnets.
3. Name two way to increase an
electromagnet.
4. What is the core of the magnet.
5. How are electromagnets used?
6. List the differences and similarities
between an electromagnet and a
regular magnet.
7. Two electromagnets have the
same current, but one has twice as
many coils as the other. Which electromagnet is
stronger? Why?
Magnetic Fields
A magnet has a North Pole and a South Pole.
When a NP of one magnet faces a SP of another
magnet, the magnets will attract to one another.
But, when the NP of one
magnet is aligned with the NP of another magnet, the
two magnets will repel. Similarly, when the SP of one
magnet is aligned with the SP of another magnet, the
two magnets will repel. At the poles, the magnetic
effect is the strongest.
Magnets are surrounded by a magnetic field.
The field may be invisible, but it exerts a force
on anything within its field. The magnetic field
is represented by magnetic field lines. Where
the magnet field is the strongest, the magnetic
field lines are closest together. Although you
can not see the magnetic field lines, they
actually exist! These field lines are very evident
when steel filings are places between two
magnets! The magnetic field lines run in complete circles from the on NP to the
other SP. The magnetic field lines can run from the NP to the SP of the same
magnets, or between different magnets.
Questions:
1. What are the lines called around the magnets?
2. What do the represent?
3. Where is this magnet strongest.
4. Where are the lines the closest.
5. What does N and S stand for.
6. What does repel mean?
7. What does exert mean?
Label the NP and the SP of each bar magnet. One of the poles has been done.
SP
SP
The earth has the
geographic North Pole
and the geographic
South Pole.
And it also has the
magnetic North Pole and
the magnetic South Pole.
The Earth emits a large
magnetic field just like a
magnet. The Earth has
magnetic field lines which
run in a circle from north to
south and back.
The Earth also has
magnetic poles which are
about 1500 km way from the geographic poles. When your compass points
North, is actually pointing to the molecular North Pole, and not the geographic
north pole. The difference between the two “North Poles” is called the
declination angle or magnetic declination. There are ways to mathematically
calculate the declination angle, and when relying on a compos, this difference in
direction must be accounted for or else you will not reach your exact destination.
The larger your distance from the North Pole, the large your declination angle.
Questions:
1. The spin of the Earth on is
access is called?
2. The path of the Earth around the
sun is called?
3. Are the geographic and magnetic
poles at the same locations?
4. If relying on a compos, what must
you calculate for accurate
measurements?
5. When the compos points N, to
which pole is it pointing
6. Where is the declination angle
the smallest?
Alex, Andie, Rob and Dorothy wanted to experiment with electromagnets.
Part One: They began their experiment by wrapping a
coil of insulated wire around 4 steel nails. They wrapped
the wire around the nails (as a group) 25 times. They
then connected the loose ends of the wire to a 9v battery.
They wanted to see how many paperclips they could pick
up with their electromagnet. They were able to pick up 3
paper clips.
Next, the students re-wrapped the coil around the 4 steel
nails, except this time they wrapped the wire around the nails 50 times! They
retested how many paperclips they were able to pick-up. They were able to pick
up 8 paperclips.
Part Two: Next, the students repeated the above experiment, but this time they
only used two steel nails instead of 4. The 25 coil magnet was able to pick-up
only 1 paperclip. The 50 coil magnet was able to pick-up 5 paper clips.
1.
An electromagnet turns _______ energy into _______ energy?
2.
What variable did the students test in the first part of this experiment?
3.
What variables did they keep constant in the first part of their
experiment? (Name at least two.)
4.
What variable did they measure in both parts of the experiment? How
did they measure it.
5.
What variable did the students test in the second part of this
experiment?
6.
What variables did they keep constant in the second part of their
experiment? (Name at least two.)
7.
Come up with a hypothesis that they might have developed for Part 1.
State your hypothesis in “If …… then ……” format.
8.
Come up with a hypothesis that they might have developed for Part 2.
State your hypothesis in “If …… then ……” format.
9.
What two factors seemed to have an effect on the strength of the
magnets in their experiment ?