# Magnetic fields

1. Oct 31, 2007

### Logarythmic

1. The problem statement, all variables and given/known data
Determine the force in z-direction on the gyrocenter of a charged particle in a diverging magnetic field.

$$\frac{\partial B}{\partial z} < 0$$

2. Relevant equations

3. The attempt at a solution

Please give me a starter. Could I use the Lorentz force in this case?

2. Nov 4, 2007

### Staff: Mentor

Is there a discussion in one's text regarding magnetic force or magnetic pressure on a charged particle?

A short answer - the effective force on a charged particle in a spatially varying magnetic field is given by:

$$\vec{F}\,=\,-\mu_m\,\vec{\nabla}B$$

Hopefully one would be able to derive this relationship.

3. Nov 4, 2007

### Logarythmic

I did it with the Lorentz Force on the guiding center and got the equation given by Astronuc but with a plus sign. I guess that the sign is dependent on the charge.