Which is stronger? eletrical or magnetic fields?

In summary, the magnetic field generated by a stationary electron's spin is very weak, but can be spectroscopically seen. It's mainly due to spin-orbit coupling, which is a result of the electron's intrinsic magnetic moment and the more conventional magnetic moment of the same electron because it is in orbit. The magnetic field at a certain distance and angle can be found using a gradient energy calculation. Compare this to the electric field, which is much stronger.
  • #1
davidong3000
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A single stationary electron's magnetic flux caused by it's spin gives it a north and south pole right? does that mean it's north pole would be attracted to the south pole of a hypothetical nearby stationary electron?

how would this attractive force compare to it's electric force of repulsion at equal distances? what's the ratio?
 
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  • #2
davidong3000 said:
A single stationary electron's magnetic flux caused by it's spin gives it a north and south pole right? does that mean it's north pole would be attracted to the south pole of a hypothetical nearby stationary electron?
how would this attractive force compare to it's electric force of repulsion at equal distances? what's the ratio?

It's a strange way of stating it the way you do, but yes, there is a "magnetic dipole interaction" between electrons. It's pretty weak, but spectroscopically visible. However, the main effect doesn't come from the magnetic dipole interaction between different electrons, but rather between the intrinsic magnetic moment of the electron related to its spin (the thing you talk about), and the more conventional magnetic moment of the same electron, because it is in orbit (a circulating charge also generates a magnetic field). This effect is called "spin-orbit coupling" and is part of the fine structure of the spectra of atoms.
 
  • #3
vanesch said:
It's a strange way of stating it the way you do, but yes, there is a "magnetic dipole interaction" between electrons. It's pretty weak, but spectroscopically visible. However, the main effect doesn't come from the magnetic dipole interaction between different electrons, but rather between the intrinsic magnetic moment of the electron related to its spin (the thing you talk about), and the more conventional magnetic moment of the same electron, because it is in orbit (a circulating charge also generates a magnetic field). This effect is called "spin-orbit coupling" and is part of the fine structure of the spectra of atoms.

so precisely how much stronger is an electrical force to a magnetic force between 2 stationary electrons? 1:100?

Remember that they are stationar but still have a magnetic field caused by their spin.
 
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  • #4
davidong3000 said:
so precisely how much stronger is an electrical force to a magnetic force between 2 stationary electrons? 1:100?

Remember that they are stationar but still have a magnetic field caused by their spin.

The electron magnetic moment equals - sqrt(1/2(1+1/2)) e hbar / (m c)

From this you can calculate the magnetic field generated by the magnetic dipole at a certain distance and angle, and the energy another (identical) magnetic dipole has.

You can find the magnetic dipole field here: http://en.wikipedia.org/wiki/Dipole

The gradient of this energy wrt the place where the second dipole is, will give you the force experienced due to the dipole-dipole interaction.

You can compare this to the Coulomb interaction.
 
  • #5
Actually (in solids at least), the "exchange interaction" that causes spins to line up is a result of the exclusion principle coupled with the Coulomb interaction. It's energetically favorable for the electron-electron two-body state to be anti-symmetric in real space, because it reduces the Coulomb interaction, but this causes the spins to be symmetric, and therefore they have to line up. This is what is perceived as the "dipole-dipole interaction" that leads to magnetism, but the pure dipole-dipole interaction is entirely too weak to account for the temperatures that we see the phase transition at.

So that should give you a sense of scale of the interaction: at equal distances, some sort of exclusion effect is far more powerful than the actual dipole-dipole interaction.
 
  • #6

Related to Which is stronger? eletrical or magnetic fields?

1. Which field, electrical or magnetic, is stronger?

The strength of an electrical field and a magnetic field cannot be directly compared as they are fundamentally different. The strength of an electrical field is determined by the amount of charge present, while the strength of a magnetic field is determined by the magnitude of the electric current. Therefore, it is not accurate to say that one field is stronger than the other.

2. Can electrical and magnetic fields be measured in the same units?

No, electrical and magnetic fields are measured in different units. Electrical fields are measured in volts per meter (V/m), while magnetic fields are measured in Tesla (T) or Gauss (G).

3. Are electrical and magnetic fields related in any way?

Yes, electrical and magnetic fields are closely related. A changing electrical field will create a magnetic field, and a changing magnetic field will create an electrical field. This phenomenon is known as electromagnetic induction and is the basis for many technological applications such as generators and electric motors.

4. Which field, electrical or magnetic, is more dangerous to humans?

Both electrical and magnetic fields can be dangerous to humans at high levels. However, in general, it is believed that exposure to high levels of electrical fields poses a greater risk to human health than exposure to magnetic fields. This is because electrical fields can cause electric shocks and damage to tissues, while magnetic fields do not have this effect.

5. Can one field exist without the other?

No, electrical and magnetic fields are interdependent and cannot exist without each other. Whenever there is an electric charge in motion, it creates a magnetic field, and whenever a magnetic field is changing, it creates an electric field. They are two sides of the same coin and always exist together.

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