Thursday, April 8, 1999
Announcements: Lab quiz next week on Lab # 8 (RC circuits)

Lecture notes:

• Current in the loop is such that it creates a B field opposite to the motion of the magnet
• If the magnet moves towards the loop, the current in the loop is clockwise;
• If the magnet is moving away, the current is counerclockwise.

• The setup is exactly oppositeas the previous example
• If the magnet is moving towards the loop, current is counterclockwise.
• If the magnet is moving away, current is clockwise.

• At t= 0 the switch is closed; Current in the left hand loop (counterclockwise) gives rise to a magnetic field, that points to the left and increases with time.
• With time, the induced current in the right hand loop must be in a direction that produces an induced magnetic field that opposes the magnetic field due to the left hand loop.
• The direction of current in the right loop is opposite that of the left loop.
• The switch had been closed for a long time and at t= 0 it was opened. The magnetic field still points to the left, but it is decreasing with time.
• The induced current in the right loop is such that it must produce a magnetic field that opposes the change in the magnetic field due to the left loop.
• The induced current in the left loop is the same as the current in the right loop. Both are counterclockwise.

• Generators: Area changes with time, but magnetic field stays constant
• F_B = B (dot product) A = BAcosq
• If the coil is being rotated, F_B =  BAcoswt

x = - dF_B/dt = + BAwcoswt
• If there are N turns;
          x =  +N BAwcoswt