Day 23: Faradays Law and Lenzs Law

  There are two wires which have same current, then we drew the magnetic field and find the magnetic force of them. We know the equation B=u/4pi*Idl/a^2 so we could figure out a new equation F=u/2pia*I_0*I_1*L.

  This experiment shows when the switch is close and the wires were charge, the wires will get closer than not charged.

  We predict there were forces made the wires get closer, but we were wrong, the alternating current made the wires get closer instead of force.

  There is the magnetic field vs. time graph.

  We calculated the magnetic flux. For the first one, the flux is 0 because A and B are parallel. For the second one, the flux is Bab because A and B are perpendicular.

  We started to do the experiment about the magnetic field in a loop.

These are the data we collected in our experiment.

  When the magnet enter or leave the loop, the dash board will change. But when the magnet stay in the loop, it did not change.

  These are the four factors we found can affect the dash board.

  We put a aluminum loop into the equipment, it can suspend.

  If the loop is cut, it can not suspend.

  We drew the forces and magnetic field on the equipment.

  We put a magnet into a magnetic tube, it will drop slower than in a non-magnetic tube.

  First, we drew two graphs of B and E. Then we find the E that the moving magnet created.

Conclusion:
  In the beginning of the class, professor gave us two wires which have same current. We found out the equation F=u/2pia*I_0*I_1*L by using another equation B=u/4pi*Idl/a^2. Then we did an experiment to understand alternating current made the wires get closer instead of forces. Next, professor showed us a very interesting experiment, metal ring will suspend on the equipment but the cut ring can not. And finally, we found the equation -wNpiR^2Bocos(wt).

Day 22: Motors & Magnetic Fields

  First, we drew the microscopic level different between ordinary pin and magnet pin. The magnetic pin is in order and ordinary pin is not.

  There are two ways to destroy a magnet which are heating and hitting.

  After professor heat the magnetic pin, this pin lost its magnetic.

  In this exercise, we found that only top and bottom have force and they cancel each other. Also, we found F = BIL and τ = 1/2 BIL^2.

    Then we did an exercise problem by using the highlight equations.

  Professor showed us an electric motor.

  There are three ways to destroy a motor.

  There are four situations of the motion of electric motor. We found that when the direction of the current change or direction of magnetic field change, the direction of rotation will also change.

  These are the answers for lab manual questions.

  We did another experiment about make a electric motor by using magnetic bar, two paper clips and wire.

  This video show how this experiment works.

  We found the equation V_h=BI/roh*q*t by using the equations E=VB, E=V_h/W and I=roh*q*V*W*t.

  We saw all compass were pointing north before professor closed the switch.

  We predict the compasses will pointing as a circle after the switch is off.

  This picture proved our prediction is correct.

  Then professor change the current direction and we found the compasses still pointing as a circle but to opposite direction.

  There is our prediction about direction of north pole of three compass.

  We found the equation for B.

  In this picture, we found the relationship between magnetic field and force is equal to (v/c)^2.

Conclusion:
  At beginning of the class, we learn lots of stuff about magnetism and how it interact inside of the magnet. Then we learned the torque is produced in a current loop. Also, we learned right land rule to find the direction of the magnetic field. Then, we learned how to destroy a magnet and a motor.

Day 21: Magnetic Forces and Fields

  First, we have a magnetic bar and a compass. We need to drew the direction of the compass around the magnetic bar. As you see, the arrows left from north and go to south.

  This picture shows when we connect the arrow together.

  Professor put iron powder to the magnetic bar.

  There are three loops in the picture, contain one pole, contain both poles and contain no pole.

  Professor rub a wire to this magnet and make the wire a magnet.

  We used equation to find the magnetic flux.

  We found the net flux is always zero.

  When we put magnet next to the oscilloscope, the dot will go different direction as the magnet moves.

  In this activity, we found out two vectors of points.

  We used the equation F=qVB to find the unit for B.

  After this activity, we found the magnitude and direction of the force exerted on the proton by the magnetic field.

  we could calculate the the force and acceleration by using the equation F=qVB.

  We could calculate the radius by using centripetal force.

  There is an exercise we did by using the equation r= mv/qB and v = 2πrf to find B.

  In this activity, we found the wire will move up and down when professor put a wire between the magnet and connect to a battery.

  There are four questions on the lab manual, and answers are:

 a. v = L/t

 b. I = q/t 

 c. F = qvB = ILB

 d. dF = IdLB

  We did an experiment called magnetic force on a current loop.

  We have to found the direction of the magnetic field and direction of force.

  Then the professor did an experiment and showed the loop will spin 90°.

Conclusion:

  Today, we started a brand new chapter; we started to learn magnet. We learned about magnetic field and magnetic force at beginning. We used compass to found the magnetic field and using iron powder to verify. Then we did lots of experiments about magnetic force.