how do you visualize magnetic field?
Answers
Answer:
The easiest way is to take a small compass and move it around within a magnetic field.
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Explanation:
The easiest way is to take a small compass and move it around within a magnetic field. The direction the compass points is tangent to the curve of the magnetic field line at any location. A nice tool for this, using a small bar magnet instead of a compass is the following I got from Arbor Scientific.
first, this seems like an impossible task since you can not see magnetic fields. However, there are several ways to do this.
1. The easiest way is to take a small compass and move it around within a magnetic field. The direction the compass points is tangent to the curve of the magnetic field line at any location. A nice tool for this, using a small bar magnet instead of a compass is the following I got from Arbor Scientific.
2. The next most popular method is to place the magnet (or electromagnet) under a piece of paper or light cardboard. You then sprinkle iron filings on top of the paper, tap the paper a couple of times, and watch the small filings line up along the field lines. You could spray clear Krylon over the pattern, keeping it in place. It is also possible to get tin-plated iron filings. These won't rust. Or, get a plastic box with iron filings in it, and place a magnet under the box. They will trace out the field lines. A variation of this is to use black sand which is simply very small particles of magnetite. Another variation, which isn't as messy, is to use the product, also from Arbor Scientific, called Mysterious Magnet Tube to see the iron filings surround the magnet in the middle. The iron filings stay contained within the cylinder. There are some other variations of this on the market, including having the iron filings suspended in oil.
3. Another method is to take your stapler, make a bunch of staples, and use them like big iron filings. Sprinkle them onto a piece of paper, like you do with the filings, or let them hang around on the magnet itself. A variation of this is to use BB's to do the same thing.
4. The most accurate method is to use a software package that will calculate the field in the space around a magnet or electromagnet and plot the field lines or display shaded areas corresponding to the strength of the field.
Ansoft Corporation had a great software package which can simulate the fields and forces surrounding permanent magnets and electromagnets. The following diagrams show the results of some simulations created using the Ansoft Maxwell 2D Field Simulator program. (Maxwell is a registered trademark). contact me to obtain a free copy of this Student Version of this program!!!
Here is a pdf of a Basic User Manual I created to help you use this Student Version. (about 825kB)
Install Adobe Reader to be able to read this file.
Helmholtz Coils or Assembly expt.gif (888 bytes)
A Helmholtz assembly is actually a specific configuration of two coils. Each coil has the same radius. Also, the coils are placed parallel to each other. The distance between the coils is the same as the radius of each coil. What makes this assembly special is that if each coil has the same current flowing through each other (by connecting them in series) and the direction of current is the same, the magnetic field within the center of the two coils changes very little as you move along the center line from one coil to the other. This is a way to create a volume with a fairly constant magnetic field throughout that volume of space.
This shows a cross section of the two coils and the field they create. The upper right dot and the lower right dot are one coil, the upper left dot and the lower left dot are the other coil. Current enters each coil at the bottom and exits at the top. The spacing between the field lines in the middle section is fairly uniform, meaning that the field strength is very constant in that area. You can easily make something like this, and test the field strength in the middle as you vary the spacing between the coils, and vary the position of the field strength sensor.
More can be done with this. If a magnet is placed within the center of the Helmholtz assembly and rotated half a turn, the response will tell you the magnetic moment. A good reference on that is here.
There are some great articles describing how to build a supersensitive magnetometer using such an assembly, especially for tracking changes in the earth's magnetic field due to magnetic storms on the sun.