Magnetism GPII: 2064-002 Friday 2pm-4pm 9 Mar 2018 Jason Roark, Johanna Cannon, Nick Haywood Introduction Using an apparatus consisting of various magnets, iron filings/soft bar, a compass, and a magnet holder, magnetic field lines in various different situations were mapped. The magnets were rearranged multiple times to observe how the magnetic fields would shift in each of the tested scenarios. The compass is necessary to verify the north and south poles of your magnets prior to experimentation. Procedure Lone Bar Magnet A lone bar magnet is placed into the magnet holder with a single sheet of white paper placed on top. (This is the standard set up for each magnetic field test performed in this experiment.) When iron filings are placed over the lone bar magnet, a standard magnetic field is mapped. The field lines make a gentle curve from the north to south poles at every point. These lines also grow in area as their origin moves further from the center of the magnet, closer to the ends. Lone U-Magnet The magnetic field of the lone U-magnet changes drastically depending on which side of the magnet the field originates. On the “inside” of the magnet, field lines are short and nearly parallel as the two poles are very close to each other. As the origin point moves towards the end of the poles, an arc begins to appear as the magnetic field is no longer held in place by the parallel poles. As the origin point moves even further to the “outside” of the magnet, the area of the field lines begins to increase dramatically until the whole field is no longer visible on a single sheet of paper; instead, only the general direction of each field is visible. Two Bar Magnets: Attractive Poles Three distinct magnetic fields are visible between the two bar magnets. Directly between the two opposing poles are a few short, nearly parallel, field lines. As the point of origin is moved slowly around the edges of the magnets a more pronounced arc begins to form as the lines travel from one magnet to the other. At some point along the magnet, the attractive force of each magnets individual opposite poles overcomes the attractive force of the opposite magnet. At this point, the field lines quite suddenly change direction and lead towards the opposite direction. As an end result, there are two “normal” looking fields (the outsides of the magnets) that trap a smaller one (the insides of the magnets facing each other) between them. As a side effect, the inside field is slightly elongated, making the arcs appear “sharper” than normal. Two Bar Magnets: Repulsive Poles Two sets of magnetic field lines become visible, separated due to the repulsive nature of the northern poles. As the magnetic fields travel from the northern poles, they very quickly encounter each other and make an incredibly sharp (nearly ninety degrees at the most extreme locations) turn to avoid each other but still travel to their corresponding southern poles. It is interesting to note that the two fields never truly encounter each other, much like two opposing electrical fields. Lone U-Magnet and Soft Iron Bar This magnetic field is incredibly similar to that of a lone U-magnet. The only real difference comes from field lines originating from the ends of the poles. Instead of a soft, smooth arc as seen with the lone U-magnet, here the field lines immediately stretch to reach the conductive soft iron bar and travel through it. Two U-Magnets: Repulsive Poles With two opposing U-magnets, it is possible to see a large variety of complex fields. While the insides of the magnets still connect straight across with each other, the outsides of the magnets now wrap around the back of the magnet to avoid crossing the opposing fields from the other magnet. The ends of the poles are split amongst each of the two possible directions; some will attempt to make the smooth arc to cross the gap straight to the opposite pole, while others take a massive trip around the back of the magnets. Conclusion Based off of the results of using multiple different magnet types, and sprinkling iron shavings on top of those varying strength magnets our experiment seemed to be very reliable based off of the information that we previously know. First when we tested the compass and the magnets everything seemed to do what they were supposed to; when the using the North part of the magnet our compass pointed South and then using the South part of our magnet our compass pointed North. The second thing that seemed to provide reliable results was that when the shavings were placed on the magnets the north electric field lines pointed to the south which holds true to theory. Lastly, theory states that magnetic field lines should not touch and this was shown during our experiment. When the electric field lines would get super close to each other they would start curving away right before touching. Overall we saw that our experimental results matched what we expected to see due to the theoretical analysis.
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