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Why did my compass work perfect at the store but stop working soon as I got home?

  1. Oct 7, 2012 #1

    Sqw

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    I bought a compass today. I tested it at the store, multiple times, spinning all which ways. It would always immediately spin itself around to accurately point north..

    It is one of those ball compasses like what's on the back of a survival knife.

    As soon as I got home it stopped pointing itself north when I would turn it. if I shake it it will sometimes point north but just as often it will wind up pointing south, west or east. I tried it outside on the porch as well. It still doesn't know the difference between north south west or east.

    When I run a magnet around it from 3 - 4 inches away from it, it spins and follows the magnet. For that reason I assume the compass works, but then why won't it point north?
     
  2. jcsd
  3. Oct 7, 2012 #2

    Andrew Mason

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    I am assuming that you don't live at the (magnetic) North Pole. So I suspect that the reason it is not working at home has something to do with the quality of the compass that you bought. Why not take it back to the store and see if it works there and if it doesn't, as I expect it won't, then you can ask for your money back.

    AM
     
  4. Oct 8, 2012 #3
    Before taking it back, you might take it away from home to see if it works. You many have some sort of magnetic anomaly at home.
     
  5. Oct 9, 2012 #4
    You probably have magnetic stuff at home which overwhelms the Earth's magnetic field.
     
  6. Oct 9, 2012 #5
    A magnet in the vicinity of a cathode ray tube televsision, for example, will be significantly affected by the magnetic field of the CRT....I could not run a tv at the steering station on my boat, for example, because the compass would be significantly deflected....
     
  7. Oct 9, 2012 #6

    Borek

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    Staff: Mentor

    Check it in other places. Around house, where there is plenty of electrical/electronic devices, there is nothing strange about the fact is doesn't work. Even outside it doesn't have to work perfectly - I know of a place in the forest (sic!) about two miles from here where compasses stop to work (for no obvious reasons - no power lines, nothing, just trees and a small pond). Apparently something is interfering with the Earth magnetic field.
     
  8. Oct 10, 2012 #7

    CWatters

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    Iron meteorite at the bottom of the pond?
     
  9. Oct 10, 2012 #8

    Borek

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    Rather unlikely, I doubt it would be unknown taking into account fact we are on the outskirts of the large city. My guess is that the pond is a clay pit (plenty of those around), so it is quite possible the ground is contaminated with some rusty remains of an old brickyard. Plus, there are plenty of WWII remains around here, which creates another possibility.

    Alternatively...

    ancient-aliens-i-dont-know-therefore-aliens.jpg
     
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