electrostatic induction and tides

Discussion in 'Physics' started by davebee, Dec 28, 2008.

  1. davebee

    Thread Starter Well-Known Member

    Oct 22, 2008
    I was thinking about how a neutral conductor that is near a charged object has a charge imbalance induced in it - charges opposite those of the nearby object bunch nearest the charged object, and the opposite side of the neutral body is left with a region charged the same as the charged object.

    It seems sort of like how the moon causes tides in the earth's oceans, with one high tide on the side of the earth nearest the moon and another high tide on the opposite side of the earth. Is this just a chance similarity, or are there any deeper principles that connect these two behaviors?
  2. mik3

    Senior Member

    Feb 4, 2008
    In the case of electric charges this is caused by electric forces.
    In the case of tides this is caused by graviational forces.
    If there is a relationship between graviational and electrical forces is a big topic. I think only god knows.
  3. triggernum5

    Senior Member

    May 4, 2008
    Using Newtonian gravity the equations for electric force, and gravity vary identically in empty space, so it makes sense that there are similarities in effect.. The electric force dwarfs gravity immensely if you look at the charge to mass ratio of a proton or electron, but gravity always works in a cumulative fashion, where as the electric force can act in opposite directions, and generally strives to be as neutral as possible as you pointed out..
  4. davebee

    Thread Starter Well-Known Member

    Oct 22, 2008
    The thing I was interested in is how the earth (or any elastic body in a varying gravitational field) is pulled into a sort of ellipsoid shape with bulges facing both towards and away from the attracting body, sort of like how a spherical conductor in an electric field due to a nearby charged object develops regions of strong charge facing both towards and away from the charged object.

    For both the electric field or the gravitational field, the math is easy if a point charge or point mass is involved, but when extended bodies are involved, it's not quite so easy for me to wrap my mind around what is happening. The moving of dissimilar charges is fairly straightforward to understand, but most explanations of the two bulges due to tides involve so much handwaving that the explanation is always sort of unsatisfying. But I was just struck by the similarity of the two cases.

    After thinking about this off and on all day, I'm starting to think that there is no simple connection between the two cases. It just happens that both cases produce lumps on both sides of the affected body.
  5. Cabwood


    Feb 8, 2009
    I also find it fascinating that principles found in one field seem to have analogues everywhere else. Ohm's law and fluid flow for example. Did you ever notice how patterns recur in different places of a chaotic fractal image? If the universe is indeed chaotic then it makes sense that a behaviour or form that you identify at one place would recur (with differences, just as with chaotic images) everywhere else you look.