Magnets And Magnetic Fields

Magnets And Magnetic Fields

Question

Experiment With Magnets

Magnets:

First, prepare two magnets lying around the house. For items such as refrigerator magnets, keep the two sides about 10cm apart and slowly bring them closer together.

1. Do you feel any force between the magnets, such as pressure or tension? Describe what you noticed. Be sure to comment on the distance between the magnets.
2. Now repeat the experiment by flipping one magnet over to the other side, starting about 10cm away and then slowly moving it closer. Can you feel the push and pull? I’ll comment again with the distance explained.
3. 3. As you may have heard, all magnets are dipoles. In other words, a magnet has two opposite ends that produce opposite physical properties. We call them the north and south ends of the magnet. Plus and minus are like electric charges, but they have essentially the same effect, so north and south are really just arbitrary designations. Below is a standard image that we have of magnets.
4. 4. Note that the ends of this horseshoe are marked with N and S for north and south. If we think of them as vectors, we can say that they have the same size but opposite directions. Like electric charges, magnetism attracts opposites and repels opposites. Therefore, when he brings together two similar poles of a magnet, they repel each other, and when he brings together two different poles of a magnet, they are attracted to each other.
5. Then bring one of the magnets close to a metal paper clip. What did you notice? Repeat the process, but make sure you have a paperclip in your hand. Comment on the effect of distance.

6. Assuming #3 used the “north” end of the magnet (but I’m not sure). Repeat step 3 at the “south” or opposite end of the magnet and record the results below.
7. You may be wondering why the opposite end of the metal paperclip behaves the same. It seems strange. With a charge, oppositely charged particles behave differently, right?!

In the case of magnets, they have opposite properties to each other, but in some cases they behave similarly. When you draw a paper clip, the paper clip contains iron, so it has “magnetism”. A whole field of research is devoted to the study of magnetic properties, but we can easily say that matter is made up of tiny magnets. If the material is magnetic and you get close to a strong magnet, the small magnet will line up like the closest magnet. A photo of it is shown below.

A case study of the magnetic properties of metals

Imagine that the image above shows an iron block, and that the little magnetic arrow that makes up the iron block is pointing north. In the left image the block is isolated and away from the magnet. Therefore, the small magnets within the magnetic iron domains that compose it are randomly oriented. The image on the right shows iron near a strong magnet, with domains aligned similarly to a nearby large magnet.

A. Note that the sentence above says “near”. Why is this?

B. Now repeat process #3 and #4 using an aluminum soda can. Below is a summary of the findings.

C. Many people think that all metals are strongly attracted to magnets, but this is not the case. Many metallic materials do not contain iron, so when the magnetic domains align, they experience a very weak attraction to magnets, as does iron. Aluminum is one such metal.

D. The next part requires a phone/tablet and a free magnetic field sensor app. All smartphones/tablets have magnetic sensors. Download one of the following free apps, install it on your phone or tablet, and move on to the next question.

e. If none of these apps work, search for “free magnetic field sensor” in the app store and you should be able to find it.

f To better visualize the magnetic domains, hold your phone/tablet close to one side of the magnet with the compass app open. Notice which end of the compass is pointing towards you. Then bring the compass to the other side of the magnet and see which side of the compass points to that side. The findings are illustrated in the sketches or photos below.

G. The compass needle should always point to the Earth’s magnetic North Pole, but when near a magnet, the needle will “align” in the same direction as the magnet, with the needle’s North Pole touching the Earth’s South Pole. If the S pole of the needle is a magnet, vice versa. Well, you may be wondering. Why does a magnet align the magnetic domains of metal and compass needles in the same way? The answer to this question is the magnetic field.

Using a compass app, magnets, the internet, or a textbook, sketch the magnetic field of two differently shaped magnets. It may not be possible to use two different shaped magnets. So feel free to use your textbook or the internet to find another textbook. Verbally describe how each magnetic field affects the compass in different regions of the field. Example: “To the left of the horseshoe magnet, the north end of the compass needle points down.” Make five such statements for five different positions around the magnet. I’ll add a sketch and description below.