# Electron confinemnet

1. Oct 9, 2014

### experimenter1

Is it possible to trap an electron in a cylinder witch is made of of negative charges. If the electron is confined, will it stay still or oscillate between the top and bottom of the cylinder? Would the charges making up the cylinder create a quantum well that the electron is stuck in?

2. Oct 9, 2014

### moriheru

Are you saying that such a construction would match with a potential well?

3. Oct 9, 2014

### experimenter1

Yes it can be a potential well, but according to a theorem called earnshaws theorem the electron would not be confined and escape, but is this true it seem as if the electron would have not much elsewhere to go except travel down and back in the cylinder where it is reppelled at both end of the cylinder also.

4. Oct 9, 2014

5. Oct 9, 2014

### Drakkith

Staff Emeritus
Yes, it is true that the electron would escape. If you surround the electron with a container of either charge, there is no electric potential difference (aka no electric field) within the container, so the electron never feels a force. It simply moves about as if the container were uncharged. Note that the classic example is a charged, hollow sphere with a charged particle inside. Other container shapes may repel the charged particle from certain places, but there will always be some way for the particle to escape. For example, an electron in your cylinder may be repelled from each end, but it will not feel a force in the radial direction and will simply drift towards the cylinder wall until impact.

See here: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/potsph.html

6. Oct 10, 2014

### e.bar.goum

A very common way of trapping charges is the penning trap, and it uses a homogenous static magnetic field, with a static inhomogeneous electric field. They are used for everything from measuring the mass of exotic nuclei, through to quantum computing, and storing antimatter. In a penning trap, paticles orbit in a epitrochoid.

http://en.wikipedia.org/wiki/Penning_trap