Question 1

A permanent magnet is a device that retains a magnetic field without need for a power source. Though many of us have experienced the effects of magnetism from a permanent magnet, very few people can describe what causes permanent magnetism. Explain the cause of permanent magnetism, in your own words.


Question 2

If we were to trace the magnetic lines of flux extending from this bar magnet, what would they appear like?


Question 3

Magnetic poles are designated by two labels: “North” and “South”. How are these labels defined? Explain how we can experimentally determine which ends of a magnet are “North” and “South”, respectively?


Question 4

Devise a method of identifying the poles of a magnet that is too large and heavy to move.


Question 5

What happens to the magnetic lines of flux emanating from a magnet, when an unmagnetized piece of iron is placed near it?


Question 6

Describe the so-called “domain theory” of magnetism, as it applies to permanent magnets.


Question 7

Define the following terms:

• Ferromagnetic
• Paramagnetic
• Diamagnetic


Question 8

A mechanic visits you one day, carrying a large wrench. She says the wrench became magnetized after setting it near a large magnet. Now the wrench has become an annoyance, attracting all the other tools in her toolbox toward it. Can you think of a way to demagnetize the wrench for her?


Question 9

Suppose we needed to shield a sensitive electronic instrument from external magnetic fields. How would you suggest we do such a thing? How can we keep stray magnetic fields away from this instrument?


Question 10

Find a magnet and bring it with you to class for discussion. Identify as much information as you can about your magnet prior to discussion:

• Location of poles
• Which pole is North, and which pole is South
• Type (metal, ceramic, etc.)

Please be careful to keep any magnets away from cassette tapes, computer disks, credit cards (with magnetic information strips) or any other form of magnetic media!


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