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.

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.)
  1. What variable did they measure in both parts of the experiment? How did they measure it.
  1. What variable did the students test in the second part of this experiment?
  1. What variables did they keep constant in the second part of their experiment? (Name at least two.)
  1. Come up with a hypothesis that they might have developed for Part 1. State your hypothesis in “If …… then ……” format.
  1. Come up with a hypothesis that they might have developed for Part 2. State your hypothesis in “If …… then ……” format.
  1. What two factors seemed to have an effect on the strength of the magnets in their experiment ?