Magnetic Fields

Professor Mason showed us what happens when iron shavings are sprinkled over a magnet. You can see that there is a wave pattern around the north and south ends of the magnet. The shavings are repelled from the north end and brought into the north end.

We used the compass to determine where the magnetic field was going at different points on the magnet.

This is the picture we were able to conclude with. Magnetic fields would go out of the north end and into the south end.

This is a large magnet that Professor Mason used for various experiments in the class.

We put surfaces around the fields at certain locations. One on the south end, one in a random location, and one around the whole thing. We found that the Gaussian surface placed around the entire system and the on in the random location would have 0 net magnetism, while the one on the south end only had fields going in, so it was negative. We also see that when you break up a magnet you make smaller magnets, until the pieces are too small and you are left with just a useless piece of material.

Professor Mason demonstrates what happens when a magnet is placed near a cathode ray. The light shown on the screen changes depending on the location of the magnet. This is because the force vector is the cross product of the velocity vector and the magnetic field vector.

In this picture we showed what would happen when the magnetic field was brought in at different locations. The Force vector was always normal to the velocity vector and the Magnetic Field Vector. From the direction of the arrows you can see that the the Force vector is the cross product of the Field and Velocity vectors. 

In the above picture we were able to determine the acceleration of a proton by first finding the force created by the velocity and magnetic field vectors and then plugging it into Newton's second law equation.

In this picture we determined what courses velocity and force vectors would take after interacting. We also derived an equation for the magnetic field and we solved with given frequency for the magnetic field on an electron.

In the above two pictures Professor Mason showed us what would happen when wire, which was charged, was also subjected to a magnetic field. In the top picture he only had a wire setup, and after the charge was turned on, the wire would jump toward us. This was because the cross product of the current and field was toward us. But in the bottom he had a circular wire above the magnet.

We were tasked with answering the question of what would happen to the circular wire setup when the current was turned on. We made a diagram on the bottom right of the board. We knew that the current would be going clockwise and we knew that the magnetic field would be pointing up. As a result we knew that the setup would turn 90 degrees in a clockwise motion away from us, and then stop. This turned out to be the correct answer.

We derived that that Force was equal to the cross product of IL and B, with L and B being vectors. I is not considered a vector in this setup.

In a situation where the magnetic field is normal to a current we find that the sum of the force vectors is 0 Newtons, since each vector has another vector which cancels it out.

We were asked to find the force at each of the locations on the half circle. We broke the circle up into 15 sections and plugged it into excel with the formula I*L*B*sinTHETA, L being the radius, and were able to come up with the force at each section of the semicircle.