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Electric Instrument & Conductor in Electric Field

  1. Feb 4, 2015 #1
    I was shuffling through the previous years question papers & I got this question !!

    '' A sensitive instrument is influenced by the strong electric field. Write a possible way to prevent this effect. Why is the electric field normal to the surface? ''

    I am not sure what the answer it. But this is what i figured out.
    It is obvious that the instrument is a conductor. Therefore it has got excess of free electrons. These free electrons will arrange them in such a way that develops an inner electric field which will cancel the electric field of the outside. There will be accumulation of negative charges on one side & positive on the other. Hence the effect of the outside electric field is neutralized.
    Electric field lines are always perpendicular to the conducting surface; because it they form any other angle with respect to the surface they would cancel each other out because of symmetry.
  2. jcsd
  3. Feb 4, 2015 #2


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    So how would you prevent an electric field from affecting the instrument? Can you change the instrument? Or do you need to keep the field from getting to the instrument?

    Have you studied anything that can keep out an electric field?
  4. Feb 4, 2015 #3


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    A hint: There is no electric field inside a conductor.
  5. Feb 4, 2015 #4
    You guys mean to say,
    Placing the sensitive instrument inside a conductor ?
  6. Feb 5, 2015 #5


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    Have you heard of shielded cables?
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