Magnetism

Basic Electricity

  • 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.

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  • Question 2

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



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  • 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?

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  • Question 4

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

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  • Question 5

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



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  • Question 6

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

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  • Question 7

    Define the following terms:

    • Ferromagnetic
    • Paramagnetic
    • Diamagnetic
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  • 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?

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  • 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?

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  • 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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