# Homework Help: How can a magnetic field move a charged particle?

1. Jan 17, 2008

### Smittens

Hi,

So in order to earn a few crucial points back from my teacher I need to prove that a magnetic field can increase the speed of a charged particle. I've made a list of a couple methods so far (see examples below) but am hoping that you all could help me think of a few more.

Now I know (or at least have been told, and can't think of an exception) that it is impossible for a magnetic field to directly increase the speed of a charged particle. This makes sense, since the force of a magnetic field is perpendicular to the particle's velocity it will only change the direction of its movement.

However, I have been considering the angle of a magnetic field indirectly speeding up a charged particle. For example (here are some of the ones I've thought of)

- A magnetic field can induce an electric field, and an electric field could move the charged particle
- A magnetic field can be induced in a ring opposite of an already existing magnetic field. If the ring in question is resting on a cylinder, the ring will be launched off the cylinder. If our charged particle in question is resting on the ring when it is launched, the charged particle will speed up as it accelerates. (This thought was based on a demonstration in class)

I'm not quite sure if this thread belongs in the right place, it's not exactly a homework question, but it is in the same idea. Any assistance would be GREATLY appreciated, and the crazier any ideas, the better! (so long as they work

Thanks,
Caleb "Smittens" Martin

2. Jan 19, 2008

### Tom Mattson

Staff Emeritus