Physlet Illustration: The Direction of Induced Current

 

 

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This simulation shows a top view of four wires and a galvanometer in the lab.  Current flowing into the + terminal, i.e., counterclockwise, will deflect the meter to the right.   During the time interval t=2 s to t=8 s a magnet is slowly pushed completely through  the rectangle from the bottom toward the top. (You can also think of  the magnet as being pushed out of the computer monitor toward the user.) Observe the meter reading during this simulation.  Which pole was inserted first? North or south? The animation starts at t=0 and stops at t=10 seconds.

Hints:

  1. Which direction is the field of a North pole?  Which direction is the field of a South pole?  
  2. Choose a direction for the normal, either into or out of the rectangle (screen).  Use the right-hand rule to determine the direction of the current.
  3. If a North pole is brought near the rectangle is the flux positive or negative?
  4. If the North pole is brought closer, does the flux increase or decrease?  
  5. Which direction is the induced current if the North pole is brought closer?  Don't forget the minus sign in Faraday's law.

Reference

See Walker, Section 23-3

Illustration written by Mario Belloni and Modified by Chuck Niederriter