# Exploring Magnetic Force: Magnet vs. Wires

• I
• nemuritai
In summary, the force of a magnet on another magnet is along the field lines because the magnetic moment of the iron filing experiences a torque that aligns it with the local field lines. However, for two wires, the force is perpendicular due to the Lorentz force being perpendicular to velocity and magnetic field. The magnetic field gradient also plays a role, with the force being alongside the field in one case and perpendicular in the other. This difference in force direction is due to the difference in the direction of the magnetic field gradient.
nemuritai
I understand the iron fillings become little magnets all pointing in the same north south direction similar to the spin aligned electrons in the permanent magnet.
Similarly, a compass near a wire traces out the magnetic field lines ie North/South.

My question is how do I reconcile the fact that the force of a magnet on another magnet is along the field lines whereas for two wires it is perpendicular? The latter is from the fact that the lorentz force is perpendicular to v and B, but why is the force of two magnets alongside the magnetic field instead of perpendicular?

Is the force alongside the B field in one and perpendicular in the other? What error have I made?

An iron filing has a magnetic moment that experiences a torque that rotates it so that its long axis lines up with the local field lines. The force on it is along the direction of the magnetic field gradient which is not necessarily along the local field lines. In the case of the bar magnets that you show in the photo, the magnetic field and its gradient are roughly in the same direction. In the case of the infinite wire the magnetic field is in the azimuthal direction but its gradient is in the radial direction.

vanhees71 and nemuritai

## 1. What is magnetic force?

Magnetic force is the force that is exerted between two magnets or between a magnet and a ferromagnetic material. It is a fundamental force of nature that is caused by the movement of electric charges.

## 2. How does a magnet work?

A magnet works by having its atoms aligned in a specific way that creates a magnetic field. This magnetic field interacts with other objects, such as other magnets or ferromagnetic materials, causing them to either attract or repel each other.

## 3. What is the difference between a permanent magnet and an electromagnet?

A permanent magnet is a magnet that retains its magnetic properties without the need for an external electric current. An electromagnet, on the other hand, only has magnetic properties when an electric current is flowing through it.

## 4. How do wires interact with magnets?

When an electric current flows through a wire, it creates a magnetic field around the wire. This magnetic field can interact with other magnets, causing them to either attract or repel each other depending on the direction of the current and the orientation of the magnets.

## 5. Can wires be used to create a magnetic force?

Yes, wires can be used to create a magnetic force by creating an electromagnet. By wrapping a wire around a ferromagnetic core and passing an electric current through it, a strong magnetic field can be created. This is the principle behind many electronic devices, such as motors and speakers.

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