CK-12-Physics-Concepts - Intermediate

http://www.ck12.org Chapter 20. Magnetic Fields

Summary

• Any magnet has two ends called poles where the magnetic effect is strongest.


• The magnetic pole found at the north geographical pole of the earth is a south magnetic pole.


• The force that one magnet exerts on another can be described as the interaction between one magnet and the
  magnetic field of the other magnet.


• Magnetic field lines go from the north magnetic pole to the south magnetic pole.

Practice

Question

This video demonstrates magnetic levitation.

http://www.darktube.org/watch/crealev-levitating-floating-flying-hovering-bouncing

MEDIA

Click image to the left for use the URL below.

URL: http://www.ck12.org/flx/render/embeddedobject/63611

Follow up question:

1. In the video, one object rests on top of the magnetic field of another. Compare the friction between these two
   objects to the friction between a saucer and a table the saucer rests on.

Review

Questions

1. The earth’s magnetic field
   (a) has a north magnetic pole at exactly the same spot as the geographical north pole.
   (b) is what causes compasses to work.
   (c) is what causes electromagnets to work.
   (d) all of these are true.
   (e) none of these are true.


2. A material that can be permanently magnetized is generally said to be
   (a) magnetic.
   (b) electromagnetic.
   (c) ferromagnetic.
   (d) none of these are true.


3. The force between like magnetic poles will be
   (a) repulsive.
   (b) attractive.
   (c) could be repulsive or attractive.


4. Why is a magnet able to attract a non-magnetic piece of iron?