Magnetic Properties (19th Day)

Spring 2015
Professor Mason
May 7 Class

Magnetic Field Sketch
In class, the first thing we needed to do was to draw the magnetic field using arrow around the magnet. We were given a random magnet, then we placed it on the white board. We had to determine the the direction of the arrow by using compass; the arrow points toward the north direction of the compass. After we finished the experiment, we found out that our magnet had two magnetic field, and the main point of the field was placed in the middle of the magnet as shown in the picture attached. Therefore, when we drew a continuous arrow, it would look like a butterfly.

Flux and Gauss Law Magnetism Proof
In class, we were asked to create a flux sketch based on our magnet; however, out magnet had a weird magnetic field, so we changed it to a normal magnet with normal magnetic field. Flux is defined as net number of poles enclosed divided by epsilon, [Flux = N/Eo], which would always be equal to zero. We also found out the unit of magnetic filed (B vector) is Tesla or Gauss; 1 Gauss is equal to 1/1000 Tesla. We had an interesting experiment involving magnet; first, we had a magnetized paper clip, then we cut it in half, and the result is each clip now has different pole. This also applies for the big magnet as shown in the picture above. If we break the magnet, it still has pole going on through the big magnet.



Magnetic Force
In class, we learned that most field, such as gravitational field and electric field, are part of force field; therefore, Magnetic Field is also a force field. Force of the magnetic field is perpendicular to electric field; the fun fact is that magnetic field also exists inside our brain. +Ve charge rotate clockwise, -Ve charge rotate counterclockwise. For electrons, we use left hand rule, and for protons, we use right hand rule. Magnetic force is defined as an equation of [F = qv x B], which B has a unit of kg/CS.

Magnet and Oscilloscope
We had an experiment in class, which it involved with an oscilloscope. We put a big magnet on top of the oscilloscope, then the graph on the oscilloscope changes. We also needed to draw a single beam with magnet, and we needed to draw the direction of the beam with magnet. We also needed to draw three vectors of magnetic field stated with the green dot on the oscilloscope; those three vectors are velocity, magnetic field, and force. The picture attached shows the direction of the arrow when we place a magnet on top or next to the oscilloscope depending on the north or south direction. It is also defined as [F = qVB sin theta], and [w = V/r], therefore [B = F/2pi qrf].

Magnetic Forces and Electric Current

 In class, we did an experiment involving this big magnet and a machine that supplies current.

 We put the wire in between the magnet; then when the professor turned on the machine, the wire started to make a curve downward as the magnet pulls the wire, although the wire is made of copper. The sketch shown on the picture above was the calculation of the wire when it is curving instead of a straight wire.

The picture above shows the calculation of the three vectors based on the setup experiment above, which concludes an equation of [dL = I dL x B]. 

Magnetic Force on a Current Loop.

 Next, we had an experiment involving a spinning wire around the big magnet. We first needed to predict what would happen to the wire around the magnet; we predicted that it was going to spin counterclockwise; however, it turned out to be spinning 90 degree as that position is most stable as the net Torque is equal to zero. It would spin the the magnetic field is parallel to the wire. The charge moves in circular motion, so that we had to use integral on the equation, [F= Integral of I B(x) dL] as shown in the above picture. The circle with the dot inside is defined as the Force moving out, and the cross with circle around it is defined as the Force moving towards us, [F = mV^2/r].