# I Magnetic field on charged cloud

1. Apr 28, 2016

### d4rr3n

An electron beam can be curved into a loop using a magnetic field with flux lines at right angles to the electron beam. These electrons have a high kinetic energy leaving the electron gun.

My question is how would a magnetic field effect motionless charged particles for example a cloud of negatively ionised gas, would it also form into a loop. I'm thinking of the auroral oval around the Earth's poles

2. Apr 28, 2016

### Simon Bridge

The effect on the beam is the same as the effect on a single electron with velocity $v$ ... the magnitude force is $F=evB$ and it points at right angles to both $\vec v$ and $\vec B$ ... the effect on a cloud of stationary electrons is the same as the effect on a single stationary electron...

(... well, there is also the effect of the electrons on each other.)

3. Apr 29, 2016

### d4rr3n

Thanks,

I have read elsewhere that a magnetic field has no effect on a stationary charged particle i.e. it does not cause a stationary charge to move or to aline to the magnetic field in any way.