# Mathematical model for interaction force between magnetic fields?

1. Jun 2, 2013

### Psinter

I wanted to know if there is a mathematical model to know the force with which a source of a magnetic field attracts or repels another source of magnetic field.

For example, the mathematical model for the electrostatic force a charged particle exerts over another charged particle is: $F = k(\frac{Q_1Q_2}{r^2})$

where:
$k$ is a constant with value 8987551788$\frac{Nm^2}{C^2}$
$Q_1$ is the charge of particle 1 in Columbus
$Q_2$ is the charge of particle 2 in Columbus
$r$ is the distance in meters between the center of each particle

So, is there a digested equation like that one but for magnetic fields?

Last edited: Jun 2, 2013
2. Jun 2, 2013

### tannerbk

Not sure exactly what you mean, but there is an analgous force law for magnetism. For a charge Q, moving with velocity v and magnetic field B, the Lorentz force law is $\textbf{F}=Q(\textbf{v} {\times} \textbf{B})$. Thus in the presence of both electric and magnetic fields, the net force on some charge Q would be $\textbf{F}=Q(\textbf{E}+\textbf{v} {\times} \textbf{B})$.

3. Jun 2, 2013

### physwizard

The analogue to an electric charge is a magnetic monopole. The fact is that the magnetic monopole does not exist (at least it hasn't been discovered so far). You will never be able to get an isolated 'North' pole or an isolated 'South' pole. Even if you break a magnet into two each half will form its own north and south poles. In other words the magnetic poles exist in pairs, an isolated magnetic pole does not exist. Nevertheless, it is still possible to approximately describe the force between two magnetic poles by a law of a similar form as Coulomb's law. It would be more accurate though to treat a magnet as a magnetic dipole; this is analogous to an electric dipole which consists of a positive and a negative charge separated by a small distance.

4. Jun 3, 2013

### Psinter

You replied and me just finishing of looking at that equation in the book. Hehe.

I'm still looking for something. What I mean is specifically for ferromagnetic materials like permanent magnets which do not posses moving electric charges.

I found this in Wikipedia: here and here

Can someone recommend some more literature on those subjects?

Yup just got that. Thanks.