Magnatism & the Things We THINK We Know About It! By Austin D. Ritchie Magnatism is a wondrous natural phenomenon. Since days before scientific discoveries were even written down the world has been playing with the theories of magnetism. In these three labs we debt with some of the same ideas which have pondered over for long before any of us were around. In these conclusions we will take a look at these ideas and find out what exactly we have learned. To understand the results of the lab we must first go over the facts about magnetism on the atomic level that we have discovered.
The way is this: magnetism is all based on the simple principle of electrons and there behavior. Electrons move around the atom in a specific path. As they do this they are also rotating on there own axis. This movement causes an attraction or repulsion from the electrons that are unpaid. They are moving in two directions though causing a negative and positive charge.
In the case though we find that these elements have a lot of unpaired electrons, in the case of iron, Fe, there are four. What happens then in the case of a natural magnet the unpaired electrons line up or the magnet in a specific mannor. That is all the atoms with unpaired electrons moving in a direction which causes a certain charge are lined up on one side and all the atoms with the opposite charge move to the other side. The atoms then start to cancel each other out as they approach the center of the magnet.
This all happens at the currie point where these atoms are free to move and then when cooled and theme tel becomes solid the atoms can no longer move (barely) causing a 'permanent " magnet (as in the diagram on the next page). This same principle can be applied to a piece of metal that has been sitting next to a magnetized piece of me tel in that over the long time they are to gather the very slow moving atoms in the metal situate in the same fashion also creating a magnet. Now that we know the basics lets begin with the experiments. Part one of the lab started us on our journey. In this part we took an apparatus with wire wrapped around it put a compass in the middle of the wire wraps.
The setup was arranged so that the wraps were running with the magnetic field of the earth, that is they were north-south. With this setup we were able to force a current through the coils of the apparatus by means of a 6 V battery and this created a magnetic field. This is because the movement of electrons (which electricity is) causes the presents of a magnetic field. Now that we know we have a magnetic field running around the compass we c began the experiment. What we did was take the magnetic field of the coils beginning with one coil and continued until we had five. What we learned from this is that with every extra coil we placed around the compass the motion that the interaction of the two magnetic fields caused increased.
These magnetic the earth's and the coils. What this means is that not only create a magnetic field but that there is a direct relationship between the amount of current and the strength of the magnetic field it creates. This leads us to the relationship: Bc u I and then by figuring in the constant we find that we can derive our first equation Bc = k I. This can also be supported by the data we collected in the lab when we see that as the measured currents went up the amount of motion went up which indicates that the magnetic field strength went up. But we don't only find this equation but we also find that as the current (or more so the magnetic field it creates) acts upon the initial magnetic field of the earth we get the motion in the compass.
This leads us to the first part of our left hand rule. The left hand rule for a straight conductor says that when the lines of flux are created they repel from the north end of the compass in a certain direction (depending on which way the charge is moving). This can be explained by our experiment's data in part one also because as we introduced the current to the earth's magnetic field we found that it created the motion on the compass. This all agrees with the left hand rule.
Lastly, we found in this part of the lab that magnetic field, represented by B, is a vector. We can say this because we know that a vector is anything that has both a magnitude and a direction. Now we need to prove that Has these features. This can be done by looking back on our lab and remembering that as we found the value for B it was the strength of the magnetic field. Now strength indicates that there is a magnitude to the field, thus giving us the first part of a vector. To finalize the theory we look back at the lab and find that as we changed the flow of the electrons in the coils the motion on the compass changed also.
What this tells us is that the magnetic field of the current passing through the wire has a direction to it also. Knowing this we can deduce that B is in fact a vector. A second, less definite, manor to find that B is a vector is to recall that in the equation B = k I we have one definite vector in the I (from earlier labs) and since we know that you much have a vector on each side of the equation in order for it to balance out and we know that k is a constant (therefore not a vector) the only possibility is that is in fact a vector. In addition to these 'required' conclusions we also found, as stated earlier, that when you have current you also have a magnetic field. This is important because it gives us another means in which to create magnetic fields other than the use of 'natural' magnets. But to put this theory application we can use the formula of Fb = B I L and say that since we know it takes two magnetic fields to cause motion (represented in this equation by F) and we know that B is in itself a magnetic field we can deduce that the value for 'I L' is in fact the value for and thus to a second magnetic field.
The next lab we conducted consisted of a factory made coil, an ammeter to find the value of the current we were creating and a bar magnet to act as a magnetic field. What we did was thrust the bar magnet N end first through one of the sides of the coil and found that this created a current. This happened because what we were actually doing was taking one magnetic field and putting it to motion thus creating another magnetic field, which in this case happened to be an electrical current. This experiment once again's deals with, obeys and exemplifies the left hand rule, but this time for a. What that means is that as we were thrusting the magnets N end into the coil we induced a positive amount of current simply because of the direction in which the LHR tells us that the current should go. Now the converse is also true in this case.
What that means is that when you either thrust the N end of the magnet out of the coil or thrust the S end into the coil we find that a negative amount of current is invoked. Our next conclusion has to deal with a combination of theories beingLenz's law and induction. Now we know from above that as we thrust the N end of the magnet into the coil we achieved a positive current and with a S end a negative current what this shows us is that there is conservation of energy here. Conservation of energy is a main part of Lenz's law.
The reason we can say that this is conservation of energy is because when a charge was induced it is the opposite (pos / neg ) of the the current that it was induced by. We can further Lenz's law by remembering that the faster we thrust the magnet into the coil the more current that was produced. This also shows us the principle of conservation of energy because the more energy put into the system the more current we got back out. This theory can be easily concluded by saying that only when you have perpendicular motion of a field can a current be produced. All these currents and fields are created by what is called induction. What this means is that we are not actually touching the physical (contact) but instead just placing them near each other so that their magnetic fields are 'touching' and the motion or force can result.
That moves us onto the last part of the lab where we used the same coil from part two and hooked it up in a system (pictured on next page) where we could measure the current strength and have our teeter-totter with an electric current running through it within the lines of the magnetic field of the coil. What we are able to do with this setup is run a current through the system creating a pair of magnetic fields on the coil and the loop (on the end of the teeter-totter). The diagram below shows the setup that was used along with a vector diagram. What this tells us is that the force, Fb or magnetic force, on the end of the TT that is inside the coil is in fact a vector. Once again that means that it has both magnitude and direction.
Now we learned last term that force is always a vector and therefore can assume that this too is a vector but there is even more evidence to support this. You see the force that is acting upon the end of the TT that is outside the coil is being acted on by the force of gravity. This gravitational force, Fg on the diagram, has the value Fb m, where 'm' is the mass of the object that is setting on the end of the TT. Since we know that gravitational force is a vector and we see that the TT is balanced out we know that the forces acting upon both sides of the TT must be equal, otherwise one side would be lowered like in the next diagram (b). Here, in b, we see the TT before the current, and therefore the magnetic fields acting causing magnetic force, has been introduced to the system. As we seethe TT is now unbalanced.
Now look back at the first diagram and notice that the vectors of Fb and the value of Fg m are equal. Since we massed the " weight' we used to uniformity and we know that gravitational force is 9. 8 m / s 2 we then know the value of Fb as well as the fact Fb is indeed a vector that the gravitational force vector. We know this because if Fb was not a vector the TT would never balance. We also notice that mathematically there is a relationship. That is that the units for the value of Fb are kg m / s 2 which we know to be velocity and therefore a vector as velocity is.
This leads us to the first of three very important equations. This equation, Fb = Bc I Lloop then gives us the experimental value for Bc which is important because this could not be measured directly in our lab. We find this value now very useful because it does not depend on any of the factory specifications for the coil which we prove to not be true later. This is the most important equation in this section of the lab for that very reason. This is because now that we know the experimental value of Bc without using the factory specs we can use that value in the next two equations to find experimental values for the factory constants and therefore prove those set values right or wrong. The next equation, Bc = k Ic Loop Lloop now serves two purposes.
One, it allows us to calculate a 'factory' value for the magnetic field, knowing the length of the loop (L), the current through the loop and coil (I) and the constant (k) from the factory. We do this so that we can compare this value to our experimental value for Bc and see how close they are. Two, is that you can plug in the experimental value for Bc and the two I's and the L and find a value for 'k' based on our data. We then compared the two numbers of each to find that in actuality the factory and the experiment disagree, . This could be due to either error on our part or on the factories but at least lets us know that we are relatively close.
Lastly, we look at the equation, Bc = u N I / L which does the same basic thing as the previous one does accept in this one we can plug in all numbers but the number of turns (N) and then solve for the experimental number of turns. Or we can plug in the factory number of turns and all the rest accept Bc and solve for that leaving us with another factory value for Bc. Once again we compare these numbers to the numbers we had previously and this time we find that the number of turns on the coil is experimentally less to a great extent and that Bc for this equation is extremely different than the ones solved for above. What this told us was that while the factory value for 'k' was relatively close the factory set number of turns is way off. All this leads us to the way that the Earth's magnetic field works. We have used this field in the lab but not defined it.
But through our experiment we can make some conclusions. What we learned combined with the diagrams and researched data that we acquired shows us that the earth does not have a bar magnet in the middle of it that is making it attract and repel things like compasses but rather that their is something else going on. After searching and thinking hard we found that the earth actually has no magnetic field in it's center but rather that the magnetic pull we feel comes from the friction (friction induces a current, earlier labs) of the out ter layer of molten earth and the top layer of its' crust and the current then creating a magnetic field as we know occurs. We can say that there is no charge in the middle because we know that the center of the earth is hot and with that it must be above the currie point, where a magnet's electrons situate and create, when cooled, a magnet. What this means is that it's too hot for a magnet to at that temperature. We also know that there is no magnet there because of the simple fact that on the atomic level a magnet cannot exist in a liquid because of the uniformity a strong magnet requires and the 'loos ness' of the molecules in a liquid, that is how free they are to move.
Now since we know that the center of the earth is molten, a liquid, and therefore a magnet cannot exist there. But this doesn't explain all of what we have learned. We also see that the magnetic 'poles' of the earth are actually not as we think of them. As the next diagram shows the earths poles are actually made up of a magnetic north and south pole and a geological north and south pole.
But these poles very. The magnetic poles are actually slightly off center to the geological poles. Along with this we can say that because of the scientists of the past we actually call the magnetic south pole the north pole and vise-versa. This isn " true to some phenomenon but rather the fact that when we think of the north pole we think of the earth's pole that the north end of a comp as (or any magnet) is attracted to.
This is actually the south end of the earths magnetic field, explaining this confusion. All of this was learned on our very difficult trip through the world of the magnet and now that we have conducted these experiments, done the research, and made these conclusions we now know that much more about the vo o-do world of the magnet!