# Stationary point charge in increasing magnetic field

1. Aug 13, 2007

### jimmyjets

hi everyone, if a stationary point charge is placed in an increasing magnetic field, is the force on the charge due to the magnetic field = 0?
because Fb = qv*B and v=0

then how would I derive the magnitude of the force on the charge due to the magnetic field with the magnetic field increasing at dB/dt?
thanks

2. Aug 14, 2007

### Mindscrape

The Lorrentz force law is actually

$$F = q \mathbf{v} \times \mathbf{B}$$

It doesn't matter how your magnetic field is changing, if you have no velocity then you will not have any magnetic force acting on the object. Magnetism, from a relative standpoint, is the study of changing electric fields, which you don't have. It is the study of moving charges. If you don't have any current running through a wire, does it have a magnetic field? No, the charges aren't moving. The same thing applies here, your charge isn't moving so there isn't a field to interact with.

The same is true if the velocity and magnetic fields are parallel, no matter how fast the particle accelerates or how much the magnetic field changes the force will be zero.

Last edited: Aug 14, 2007