# Magnetic force on a conductor

• eightsquare
I was wondering how the nuclear force can hold the protons in place. If the protons are subject to force and accelerate they can drag the neutrons along with them. The nuclear force is very strong compared to the electromagnetic forces from magnetic fields in your lab. It's like picking up an apple: you pick up the whole apple and not just the shell (where you apply the force), as the internal forces (holding the apple together) are very strong compared to the force of you, lifting the apple.

#### eightsquare

When a conductor carries current, due to Lorentz force, the conductor experiences a force. However I was wondering what causes electromagnetic induction. Moving a conductor in a magnetic field causes its charges to experience a Lorentz force, but unlike the case of the current, here both the positive and the negative charges are moving, so both of them feel a force. So how is a current set up? Why don't the positive charges move?

The opposite charges will be under the action of forces in opposite directions. The positive charges won't move because they are attached to the fixed nuclei. The electron's are free to move

Yes, they both feel Lorentz forces. And if they are "free", they both move.
The motions will be in opposite directions so the currents will add up.

In a metal the positive charges (ionic cores) are bound together in the lattice and the Lorentz force cannot "move" them. The electrons are the only free charge carriers in this case.

What do you mean 'in a metal the positive charges are bound together in the lattice'?

The positive charges are fixed. The nuclei of the atoms are not free to move around. If they were free to move you would have a liquid, not a solid

Conductors only have free electrons because of their electronic configuration.Positive charges in conductors are present inside the nucleus of the atom where they are bound by strong nuclear forces and this nucleus is constrained inside the metal lattice and hence these positive charges cannot move across the conductor .So the positive charges also experience lorentz force but that force is not enough to move the protons or the nucleus.

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The nuclear force binds the protons and neutrons together in the nucleus. But this is not so relevant here. The nucleus (positive) could move under the effect of the Lorentz force if it were not bound to the other nuclei in the crystal. They also are more massive than the electrons so even if they were free their motion will be much slower.

In a ionic solution both positive and negative ions (their nuclei included) move under the effect of external fields.

Ok thanks. I was wondering how the nuclear force can hold the protons in place. If the protons are subject to force and accelerate they can drag the neutrons along with them. Could you please elaborate on how 'if they were not bound to the other nuclei in the crystal'? Which force binds them exactly?

eightsquare said:
Ok thanks. I was wondering how the nuclear force can hold the protons in place. If the protons are subject to force and accelerate they can drag the neutrons along with them.
The nuclear force is very strong compared to the electromagnetic forces from magnetic fields in your lab. It's like picking up an apple: you pick up the whole apple and not just the shell (where you apply the force), as the internal forces (holding the apple together) are very strong compared to the force of you, lifting the apple.

Could you please elaborate on how 'if they were not bound to the other nuclei in the crystal'? Which force binds them exactly?
If you try to move a nucleus in a solid, the electrons surrounding this nucleus will move as well (to stay in their orbits), but then they get repelled by electrons of other atoms nearby.
In addition, there are electrons in chemical bonds, keeping the atoms together and at a fixed distance (again, due to electromagnetic forces), but that needs some quantum mechanics for a proper description.

Okay thanks!

## 1. How does a magnetic field affect a conductor?

When a conductor, such as a wire, is placed in a magnetic field, it will experience a force. This force is known as the magnetic force and it is caused by the interaction between the magnetic field and the electric charges in the conductor.

## 2. How is the direction of the magnetic force determined?

The direction of the magnetic force on a conductor is determined by the direction of the magnetic field and the direction of the current flowing through the conductor. The force will act in a direction perpendicular to both the magnetic field and the direction of current flow.

## 3. How is the magnitude of the magnetic force calculated?

The magnitude of the magnetic force on a conductor can be calculated using the equation F = BIL, where B is the magnetic field strength, I is the current flowing through the conductor, and L is the length of the conductor within the magnetic field.

## 4. Can the strength of the magnetic force be increased?

Yes, the strength of the magnetic force on a conductor can be increased by increasing the strength of the magnetic field, increasing the current flowing through the conductor, or increasing the length of the conductor within the magnetic field.

## 5. How does the angle between the magnetic field and the conductor affect the magnetic force?

The angle between the magnetic field and the conductor can affect the strength of the magnetic force. When the conductor is perpendicular to the magnetic field, the force will be at its maximum. As the angle decreases, the force will decrease proportionally until it reaches zero when the conductor is parallel to the magnetic field.