Why does electrostatic force move water but not magnetism?

In summary, the conversation discusses the surprising ability of a plastic shopping bag to push and pull tap water using electrostatic force. This force is different from magnetic force, which cannot have a noticeable effect on water due to its small magnetic dipole moment. On the other hand, the electric dipole moment of water allows for a moderate electrostatic field to have a small but noticeable effect. The conversation also touches on the concepts of electric and magnetic moments and their role in affecting different systems.
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student34
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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.
 
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  • #2
Water is slightly diamagnetic, meaning it is repelled by a magnetic field.
 
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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.
 
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Thanks everyone, it makes sense now.
 
  • #6
student34 said:
why that doesn't happen with magnetism.

Watch at 0:57

 
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1. Why does electrostatic force move water but not magnetism?

Electrostatic force is the attraction or repulsion between electrically charged particles, while magnetism is the force of attraction or repulsion between objects with magnetic fields. Water molecules are electrically polar, meaning they have positively and negatively charged ends, making them susceptible to the electrostatic force. Magnetism, on the other hand, only affects objects with magnetic fields, such as iron, nickel, and cobalt.

2. How does electrostatic force move water?

Electrostatic force can move water through a process called electrophoresis. This involves applying an electric field, which creates a force on the charged particles of water molecules, causing them to move in a particular direction. The strength and direction of the electric field determine the movement of the water molecules.

3. Can magnetism move water at all?

No, magnetism cannot move water. As mentioned earlier, magnetism only affects objects with magnetic fields, and water molecules do not have a magnetic field. Therefore, magnetism does not have any influence on the movement of water molecules.

4. Why is electrostatic force stronger than magnetism in moving water?

Electrostatic force is stronger than magnetism in moving water because it acts directly on the charged particles of water molecules, while magnetism only affects objects with magnetic fields. The strength of the electrostatic force depends on the magnitude of the electric field and the charge of the particles, making it a more powerful force for moving water.

5. Are there any real-life applications of electrostatic force moving water?

Yes, there are many real-life applications of electrostatic force moving water. One example is electrophoresis, which is used in laboratories to separate and analyze molecules based on their size and charge. Another application is electrostatic precipitators, which use electrostatic force to remove particulates from industrial exhaust gases. Additionally, electrostatic force is used in inkjet printers to propel ink droplets onto paper, and it is also used in some types of air and water purifiers to attract and remove pollutants.

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