Module 7: Magnetic Field Mapping of Bar Magnets
A compass is a tool to show the direction of the net magnetic field at the location of the compass needle. As long as there are no other significant sources of magnetic fields nearby, the compass will point North. During the first week of our exploration of magnetic fields, you will intentionally bring a magnet near a compass needle and use the needle to map out the magnetic field produced by one or two strong neodymium magnets in multiple arrangements. In week two, you will use the IOLab to measure the strength of the magnetic field at several distances from a single magnet to quantitatively explore the relationship between B and r.
Objectives
This first week, you will:
- Use a compass to observe how the direction of the magnetic field changes as it is moved around one or more magnets.
- Create a map of unit vectors pointing in the direction of the net magnetic field at several observation locations around one or more magnets.
- Use the magnetic field unit vectors to draw magnetic field lines according to the drawing conventions discussed in the instructions.
Read the Lab Document Download Lab Document
For this first week, you will read up to the section on page 6 titled, "Dipole field strength measurements."
Lab Set Up and Data Collection
Lab Materials and Setup Videos -
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Lab Materials
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Setup Videos |
Reversing the Polarity of a Compass Needle
Check that the dark end of your compass needle points towards geographic North. If instead the lighter end of the compass needle points north, then follow the instructions in this video for reversing the polarity of the compass needle.
Report your findings.
You will scan and submit several maps of the magnetic field surrounding a collection of one or more magnets, as described in the instructions. Submit these maps as a single PDF file containing five pages in the sequence indicated below:
- Two magnets touching end to end, making one large magnet. (6 total field lines)
- Two magnets separated 10cm, along their horizontal axis, with similar ends facing each other and are repulsive. (6 total field lines, around just one of the magnets).
- Two magnets separated 10cm, along their vertical axis (so the horizontal axis of each runs parallel, with N above N and S above S).
- Two magnets separated 10cm, along their vertical axis (so the horizontal axis of each runs antiparallel, with N above S, and S above N).
- A paper divided into 4 quadrants, with sketches of each case above at a reduced scale showing the full magnetic field, including the unmeasured sections using symmetry as a guide (as discussed in C.Q. 3)
Discussion Posting
Use this discussion board to discuss your findings and provide assistance for your fellow lab students. Upload a magnetic field lines map for two magnets using any orientation of your choosing. Try something unusual and comment on the maps produced by another student.
Upload and Submit
Upload your pdf containing the five pages as described above in "Submit your findings," to the assignment Lab 7 - Magnetic Field Maps by Sunday at 11:59PM EST.