Introduction :: Purpose :: Review of Literature :: Hypothesis :: Background Information :: Materials Needed :: Procedure :: Results :: Discussion :: Works Cited :: Links:: Return to Research Page
You Repulse Me: An Insight Into Magnetic Repulsion
by Highly Esteemed Physicists Katherine Ann Alexander, Kaitlin Jean Eichelberger, and Tonya Rae Hahn
We based our experiment off of the Maglev trains going in around Japan and Germany. The Japanese have developed a repulsion system that has wheels as well as the magnetic railways. When the train gets up to 100 km/h it levitates above the U-shaped tracks. The Germans have also begun experimenting with Maglev’s. They use a much smaller T-track that takes up less space but cannot be derailed. But, both use the same basic principles. The train rides on an electromagnetic wave that pushes and pulls the train. The electromagnets in the guide system change polarity with alternating current passing through them. Raising the frequency of the current speeds up the train, and reversing the poles of the magnetic field act as brakes and are able to stop the train without friction. Studies have shown that magnetically levitated trains (maglev) are capable of running at speeds up to 500 km/h, as opposed to normal trains that average about 300 km/h (Rigden 852). Our experiment will determine the amount of force magnets can hold which may lead to some extensive knowledge about the amount of force Maglev’s will be able to use, possibly resulting in better production. top
Evaluate the function of the
distance between two repelling magnets in relation to the force placed upon
them.
In the book, superconductivity was first observed by H.K. Onnes (1853-1926) in 1911 when he cooled mercury below 4.2K. He found that at this temperature, the resistance of mercury suddenly dropped to 0. In general, superconductors become superconducting only below a certain transition temperature, usually within a few degrees of absolute 0. Resistivity of superconductors is less than 4x10^-25 ohm meters, which is over 10^16 times smaller than that of copper and is considered 0 for practice.
In large magnets, a great amount of energy is needed just to maintain the current, and energy is wasted as heat. The use of higher-temperature superconductors would enable motors and generators to be much smaller (1/10 the size today) if superconductors can be developed to sustain large currents. Either a small conductor can be levitated by using an electromagnet to generate the varying magnetic B field, or a small magnet can be levitated by rotating a conductor underneath it. The currents induced in the superconductor experience no resistance. Just like that maglev trains we studied earlier.
Levitation can be defined as maintaining a body in stable equilibrium without mechanical contact with the earth; magnetic levitation implies that this can be done with magnetic fields (Giancoli 537).
We plan to build a device made of two pieces of wood connected by a hinge with one magnet on the bottom plank and another on the angled plank. The bottom magnet due to the natural repulsion of magnets will levitate the top piece, and we will try to decrease the distance by adding a weight (most likely sand) to the top plank. A laser pointer will also be formatted to the top plank in order to measure the distance change when force is added. top
The force (N) placed on the magnet is exponentially related to the distance (cm) between the magnets because as the distance approaches 0, force will become increasingly larger and distance will decrease. The function between the distance (cm) and the force (N), using the formula F=ma, m=mass (kg), a=acceleration (9.8m/s/s) of two repelling magnets will represent an exponential curve, with the limit as the force approaches infinity equal to 0. We believe this because as repelling magnets get closer together, they seem to need an increasing amount of force to make them travel the same distance. top
We based our experiment off of the
Maglev trains going in around Japan and Germany. The Japanese have developed a
repulsion system that has wheels as well as the magnetic railways. When the
train gets up to 100 km/h it levitates above the U-shaped tracks. The Germans
have also begun experimenting with Maglev’s. They use a much smaller T-track
that takes up less space but cannot be derailed. But, both use the same basic
principles. The train rides on an electromagnetic wave that pushes and pulls the
train. The electromagnets in the guide system change polarity with alternating
current passing through them. Raising the frequency of the current speeds up the
train, and reversing the poles of the magnetic field act as brakes and are able
to stop the train without friction. Studies have shown that magnetically
levitated trains (maglev) are capable of running at speeds up to 500 km/h, as
opposed to normal trains that average about 300 km/h (Rigden 852). Our
experiment will determine the amount of force magnets can hold which may lead to
some extensive knowledge about the amount of force Maglev’s will be able to
use, possibly resulting in better production. top
When we began our experiment, we found that the strength of the hinge
connecting the two boards was not strong enough to keep the magnets, which would
naturally try to attract to each other, from bending the pieces of wood so that
the magnets stuck together when they were oppressed by a heavy force.
Therefore, we modified our experiment and glued two lengths of wood to
both sides the bottom piece of our experiment, pointing up to align the top
piece with the bottom. When the magnets stuck together, we noticed that they always
attracted to the same side, because of this, we placed one length of wood on
that side directly next to the magnets and the other length on the opposite side
farther down the apparatus to balance it. We
sanded these lengths of wood in order to provide less resistance where the upper
arm swings down, and therefore reduce a portion of the uncertainty.
Our results, upon
our evaluation the function of the force (N) placed upon the magnets in relation
to the distance between the two magnets, resemble an exponential like curve
function relating the two.
Force on magnets vs. Distance between Magnets
There appears to
be a visible amount of error in our data. This
is due to the wide range of uncertainty in our measurement of the force.
When measuring the length of each weight group on the wall, the
difference in the points varied to as much as 10 cm, making the approximate
uncertainty for the length at least ± .004 meters.
For the mass, the hundredth gram place was estimated, making the minimum
uncertainty for the mass ±.00001kg. However,
since we can not be sure of the accuracy of the scale and because a couple of
pebbles may have been dropped in the process of the experiment, a more realistic
estimation of the uncertainty of the mass would be approximately ±.005 kg.
For the uncertainty of gravity, we will use ±.01 m/s/s due to the fact
that gravity has been measured at both 9.8m/s/s and 9.81 m/s/s.
The total uncertainty equated to about ±.019. top
After reviewing our results, we found them to be nearly congruent with our hypothesis. In our hypothesis, we predicted that the relationship between the distance between the magnets and the force placed upon them would represent an exponential function. This seemingly turned out to be true. Therefore, if our results are valid, we can conclude that, as repelling magnets get closer together, their force upon one another increases exponentially. There were, however, many places in our procedures that could be improved upon.
Sometimes we found that our data points from different weight groups were overlapping. This part of the error could be made less if the experiment was farther away from the wall. During our experiment we chose where to put our magnetic force repulsion device where it was because of the laser pointer and the ceiling. The laser pointer we were using had a diameter of about one centimeter when it shone on the wall. We estimated where the exact point was by placing a dot in the middle of where the light shone. In future experiments, it would be more accurate to get a laser that has a very small diameter. Also, in the future we would find an available wall that is taller so that we will be able to move farther away. Or, in order to avoid the whole laser/distance from wall uncertainty, we could simply obtain a devise that measures the exact distance between the magnets, this would decrease uncertainty greatly.
Although we oiled the hinge and sanded the wood, we believe that it is possible to have less resistance on the devise than what we had. Wood is not the smoothest in texture, so in the future we would have plastic or metal in order to gain more accurate data. Also, we would try a different hinge material to see if that worked more efficiently. This material could be cloth glued on or another bendable material.
Another way to make our data better would be to try a greater variety of weights to gain more data points. This would enable us to find more points along the curve so that the curve of the graph would be closer to the actual curve. We could also take more than seven points for each weight.
For future studies, we could test the different strengths of magnets or different shapes to see how the results may vary. Also, we could try turning our bar magnets different directions, horizontally and vertically to analyze the difference between the two. By doing this we can determine different graphs of distance vs. force to determine the most efficient magnet to use for the amount of force applied or which type of magnet would apply the most resisting force for a certain distance. top
Giancoli, Douglas C. Physics: principles with
applications-5th edition.
New Jersey: Prentice Hall, Upper Saddle River, 1998.
Hoadly, Rick. “Magnet Man” The Hoadly Family.
2005. http://my.execpc.com/magnets.html
Rigden, John S. Macmillan Encyclopedia of Physics-2
Macmillan Reference USA, Simon and Schuster Macmillan New York: Prentice Hall Int.
1996.