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.