### Magnatism & the Things We THINK We Know About It!

By Austin D. Ritchie

Magnatism is a wonderous natural phenomanon. Since days before

scientific discoveries were even written down the world has been playing with

the theories of magnatism. In these three labs we delt 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 magnatism on the atomic level that we have discovered. The way magnatism

works is this: magnatism 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 repultion from the electrons that are unpaird. They are moving in

two directions though causing a negative and positive charge. In the case of

magnatism 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 the

metel 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 magnatized piece of metel in

that over the long time they are togather the very slow moving atoms in the

metal situate in the same fassion 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 parralel 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 6V

battery and this created a magnetic field. This is because the movement of

electrons (which electrisity is) causes the presents of a magnetic field. Now

that we know we have a magnetic field running around the compass we cbegan the

experiment. What we did was take the magnetic field of the coils begining 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 feilds

being the earth’s and the coils. What this means is that not only does

electicity 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 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 mathmaticly 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 magnatude and a direction. Now we need to prove that B

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 magnatude 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 infact 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 possiblility is that

B is infact 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 into

mathmatical 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 magnectic field we can deduce

that the value for “I L” is infact the value for and thus equivilant 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 antother magnetic field, which in this case happened to

be an electical current. This experiment once agains deals with, obeys and

exemplifies the left hand rule, but this time for a celenoid. 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 combonation of theories being

Lenz’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 magentic 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 objects

togather (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 infact a vector. Once again that

means that it has both magnatude and direction. Now we learned last term that

force is always a verctor 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 on

eachother causing magnetic force, has been introduced to the system. As we see

the TT is now unballanced. 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/s2

we then know the value of Fb as well as the fact Fb is indeed a vector that is

ofsetting the gravitational force vector. We know this because if Fb was not a

vector the TT would never balance. We also notice that mathmatically there is a

relationship. That is that the units for the value of Fb are kg*m/s2 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 equatins to find

experimental values for the factory constants and therefore prove those set

values right or wrong.

The next equation,Bc = k * Ic * Iloop * 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 actuallity the factory and the experiment disagree, but

minorly. 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 previosly 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 extreemely 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 actaully 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 outter 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 extreemly 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 possibly

exhist 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 “loosness” 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’t

due to some phenomanon 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 compas (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 conclutions we now know that much more about the voo-doo world of

the magnet!

Category: Science