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Why does electrostatic force move water but not magnetism?

  1. Feb 26, 2015 #1
    So I was surprised to notice that my plastic shopping bag was able to actually push and pull tap water significantly far with its electrostatic force. But when I put a magnet near the water nothing happened. What makes the electrostatic force so different from magnetic force; isn't it just two kinds of the same force (electromagnetic force)?

    I know the basics about the properties of water (atomic structure, polarity, intermolecular forces [such as hydrogen bonding] that cause adhesiveness and cohesiveness in the water, etc) and electrostatic force (and electromagnetic force which is perpendicular to moving charges).

    None of my basic knowledge even comes close to explain what pushes and pulls the water and why that doesn't happen with magnetism.
  2. jcsd
  3. Feb 26, 2015 #2


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    Staff: Mentor

    Water is slightly diamagnetic, meaning it is repelled by a magnetic field.
  4. Feb 26, 2015 #3
  5. Feb 26, 2015 #4


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    In short the magnetic field of the magnet is not big enough to produce any noticeable effect. This is because the water molecules have a small magnetic dipole moment therefore they need a big magnetic field to affect em. On the other hand the water molecules have not so small electric dipole moment so a moderate electrostatic field can have small but noticeable effect on them.

    The electric dipole moment is a measure of the separation of positive and negative electrical charges in a system of electric charges, that is, a measure of the charge system's overall polarity

    The magnetic moment of a magnet is a quantity that determines the torque it will experience in an external magnetic field. A loop of electric current, a bar magnet, an electron(revolving around nucleus), a molecule, and a planet all have magnetic moments.
  6. Feb 26, 2015 #5
    Thanks everyone, it makes sense now.
  7. Feb 26, 2015 #6


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    Science Advisor

    Watch at 0:57

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