# Free electrons

1. Nov 2, 2009

### Niles

Hi all

Is a free electron (with momentum p = hbar k) still free if it is in an electric field? I.e., is the momentum is given as p = hbar k?

2. Nov 2, 2009

### Bob_for_short

No, it is not free any more. No, the kinetic momentum is different and may well be uncertain because there is no k any more. It depends on the form of the external electric field: uniform, Coulomb, etc., as well as on the problem you solve: stationary states or transitions.

Last edited: Nov 2, 2009
3. Nov 2, 2009

### fatra2

Hi there,

Under the action of an electric field, the momentum of a free electron will vary.

Cheers