Is the motion of a charge across junction momentum conserving ? Why or why not ?

Explanation

When an electron approaches a junction, in addition to the uniform electric field E facing it normally. It keep the drift velocity fixed as drift velocity depnds on E by the relation drift velocity
`v_(d)=(eEtau)/(m)`
this result into accumulation of charges on the surface of wires at the function. these produce additional electric field. These fields change the direction of momentum. Thus, the motion of a charge across junction is not momentum conserving.