Lab
Forces Between Ceramic Magnets
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Purpose
The purpose of this experiment is to investigate the strength of the magnetic field between two circular, ceramic washers by placing washers on top of a "floating magnet" and recording the distance of the gap between it and two stationary magnets. The magnetic field of an ideal dipole can be calculated with the equation:
where µ
_{o}
is the permeability of free space and µ is its magnetic moment. For the purposes of our experiment, we are not investigating the values of these constants, but whether we can replicated the relationship that B
_{axis}
is proportional to 1/d
^{3}
.
Equipment
Each group will be provided with the following equipment:
three round ceramic magnets with 3/8" diameter holes
32 washers
one aluminum rod with a 3/8" diameter
one test-tube clamp
one ring-stand
one c-clamp
one triple beam balance
one centimeter ruler
Carefully set up your equipment as shown in the example station. Make sure that you treat the magnets with respect. Their domains can be damaged if they are dropped or handled carelessly. Also keep these magnets AWAY from electronic devices as permanent damage will most likely occur. These magnets are strong.
Begin by measuring the mass of a single magnet which will "float" above the other two. Then mass all 32 washers and obtain an average mass for one washer.
Next "float" the single magnet above the other two aligned magnets. Carefully place all 32 washers on top of the "floating" magnet and record the distance separating the two sets of magnets. Then, in groups of 4, remove the washers and continue to record the separation distance. When all washers have been removed, again record the separation between the two sets of magnets.
Repeat the process TWO additional times, resulting in a total of three trials of measurements. Fill in your values in the chart below.
Data Table
After all of your data has been collected, graph your results using the spreadsheet
1-ceramicmagnets.xls
. Each round will be represented by a separate trend line on the first graph of
Mass vs Gap Distance
.
Analysis and Conclusions
What was the average mass of one washer (g)?
What was the mass of the floating magnet (g)?
Based on your R
^{2}
values, which round of trials had the best results for the graph
Mass vs Gap Distance
?
What was EXCEL's regression equation for this round of trials?
What was EXCEL's regression equation for your graph of
Weight vs 1/(Av Distance)
^{3}
?
Within the "linear portion" of your graph of
Weight vs 1/(Av Distance)
^{3}
, compare the distances supporting the weight with 4 washers and the weight with 20 washers.
washers
weight
distance
4
20
Based on your products: W
_{4}
*(d
_{4}
)
^{3}
and W
_{20}
*(d
_{20}
)
^{3}
, would it be appropriate to say that your experiment supported the hypothesis:
"the magnetic force between two magnets is inversely proportional to the cube of the distance between the magnets"?
Answer
yes
or
no
as well as
explain your rationale
.
Adapted from:
http://www.wbabin.net/science/michaud2.pdf
page 5
http://ocw.mit.edu/NR/rdonlyres/Physics/8-01TFall-2004/F7EF1F68-A8F0-4706-B35A-B5F41E5AF3EA/0/exp03.pdf
page 1
http://faculty.eicc.edu/kjohnson/labbook/physics/34pmagnet.pdf
page 1
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