Planning/Miscellaneous

• Finding center of gravity:

  • Make 3 small holes on edge of shape
  • Suspend shape freely on one of the holes, suspending a plumb line in front of the shape
  • Mark top and bottom of plumb line
  • Repeat steps 1-3 for other 2 holes
  • Join the markings, CG is the intersection of the 3 lines
• How alternating current causes an induced emf:

  • Alternating current produces a magnetic field that constantly changes in direction as current changes
  • This creates a constantly changing magnetic flux linkage between (object 1) and (object 2)
  • According to faraday’s law, this induces an emf in (object 2)
• What happens when there is direct current in AC circuit:

  • There is only momentary change in magnetic flux when the switch is opened or closed
  • This thus induce momentary emf
• Using compass to find magnetic field lines:

  1: Place a plotting compass near the current carrying wire.

  2: Mark a dot on the north and south ends of the compass needle with an N and S respectively.

  3: Reposition the compass to a new position such that the South pole of the needle is pointing to the N marking of the previous position.

  4: Mark a dot with N which is the North pole of compass needle in the new position.

  5: Repeat 3 and 4 until the path of one magnetic field line is traced out.

  Step 6: Start at a different point further from the wire and repeat to plot other field lines.