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SMC|Academic Programs|Physical Sciences|Measuring Magnetic fields

Measuring Magnetic fields

Part A

Place a bar magnet in the middle of a page. Draw an outline around it so that it can be replaced easily in the same position. Mark the north and south ends within the magnet outline.

Connect the magnetic field probe to the ULI and open the experiment file "Lo Gain (mT)". Mark and label a number of positions out from the poles of the magnet at 1 cm intervals, and also around the magnet's sides to get a good cover of the area on the page. You should have 25 or more points marked.

Magnetic Lab Image

At each of the points you will measure the magnetic field using the magnetic field probe, as shown above. Varying the orientation of the probe will give different magnitude readings because it only detects the component of the magnetic field that is perpendicular to the white dot on its face.  Find the true field magnitude by clicking collect and finding the orientation of the probe that gives a maximum reading (by watching the red line on the graph). Continue to collect data for 5 - 10 seconds at this maximum value. BEFORE removing the probe from the point draw an arrow on the page to show the direction the dot on the probe was facing. 

Magnetic Lab Image 2

Select and highlight the region of the graph that was roughly a maximum and use the "Statistics" function under the menu choice "Analyze" to find the average recorded magnetic field value. This will be your "true" magnetic field value. Record this on the page. Continue for your other points around the page. 

Does a pattern of directions seem to arise? Explain.



Is there a pattern to how the magnitude of the magnetic field varies? Explain.



Part B

Place the bar magnet so it is just half on the end of a piece of paper. Draw its outline and an axis coming out from its end and down the center of the page. Mark a centimeter scale on this axis, with zero at the center of the magnet.

Magnetic bar Lab

Using the force probe as in Part A, record the magnetic field values as you move directly out from the magnet. You should record the magnetic field at intervals of 0.5 cm when close to the magnet, but increase to intervals of 1cm as you get further from it.

Next enter your data into the "Graphical Analysis" program and complete an "Automatic Curve Fit" to find the functional behavior of the magnetic field as a function of distance from the magnet. Print out your data and graph. 

What is the functional dependence you found?



Summarize your findings about the magnetic fields of bar magnets.