 We discovered that, as time passed, we had to move the paper clip ever closer to the north marking in order to cause the compass needle to deflect to NNW.
When trying this same experiment with other paper clips, we found that the rate of relaxation varied. We used six different paper clips. The results are shown in the chart below: |
Time elapsed
(in minutes) |
Distance From North Marking
(in millimeters) |
| |
Clip A |
Clip B |
Clip C |
Clip D |
Clip E |
Clip F |
Averages |
| 0 |
102 |
90 |
80 |
79 |
83 |
76 |
85 |
| 20 |
95 |
90 |
76 |
77 |
82 |
74 |
82 |
| 40 |
90 |
86 |
73 |
75 |
82 |
71 |
80 |
| 60 |
85 |
83 |
70 |
74 |
81 |
68 |
77 |
| 80 |
85 |
80 |
70 |
73 |
80 |
65 |
76 |
| 100 |
80 |
80 |
67 |
73 |
78 |
63 |
74 |
Here is a graph showing the results for paper clips B, D, E, and F. Notice that the rate at which each paper clip relaxed varied. Although some paper clips relaxed a substantial amount, others seemed to relax very little. Some paper clips seemed to relax in sudden steps while others relax more gradually.
This graph shows the results averaged for all six paper clips. Although there is variation in the rate at which the paper clips relaxed, the general trend is that the greater the time from when the paper clip was magnetized, the closer it needs to be brought to the compass needle to achieve the same deflection to NNW. This shows that the overall strength of the magnetic field is decreasing over time. To compensate for this we must move the paper clip closer so that the needle is in an area where the paper clip's magnetic field is stronger.
-
Repeat the experiment by changing the mass of the paper clip. You can use a larger clip or put two or three paper clips together in a bundle.
- Repeat the experiment, but change the number of turns of the coil of wire used to wrap the paper clip when creating the electromagnet. You will need to start with a longer piece of wire and wind a second, and maybe a third layer on top of the first.
- We checked the paper clips over a period of several days. They never completely lost their magnetization, even after a week. What do you find over a long period of time?
This experiment can give you an idea of how magnetic relaxation works. But we've left out some details, and there are some important differences between what happens with our paper clips and the part magnetic relaxation plays in NMR. For more of the story read Digging Deeper.
|
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