# Why would electrons cross a cross section when there is no potential difference?

There is a cross section , it's said that electrons move from left to right and vice versa, and the total sum of the electrons crossing this section from left to right is equal to the ones crossing from right to left.

When we have potential energy (a battery connected to 2 sides of this section) electrons going from left to right are more than the ones going from right to left, and then there will be electrical current.

My question is, why would electrons move when there is no difference of potential?

Edit : electrons that move are free electrons.

• what is the medium or material the electrons moving you are referring to? – HelpMee Jun 21 '17 at 13:11
• @doncarlos it's not pointed, i just know that free electrons move in that cross section – parvin Jun 21 '17 at 13:13
• The flow is always from higher to lower potential. no potential no flow. – HelpMee Jun 21 '17 at 13:26
• Brownian motion applies to electrons in a metal pretty much the same as to molecules in a gas. – The Photon Jun 21 '17 at 15:24

First, there is a small change you need to make.

electrons going from left to right are more than the ones going from right to left, and then there will be NET NON-ZERO electrical current.

With that done, you should be aware that free electrons, like any particle, are incapable of being perfectly at rest (except at absolute zero). That is, they will exhibit random motion, usually called thermal motion. With no potential applied, the average overall, or net, motion will be zero, and so will the current.

• @parvin Thanks for the selection, but please be aware that it's a good idea to hold off on giving points for 24 hours or so. On the one hand, early selection inhibits others from replying. On the other hand, there is always the possibility that one of those answers would be (gasp!) better than mine. Not that that's possible, of course. Just saying. – WhatRoughBeast Jun 21 '17 at 13:47

Electrons move. (Don't ask me why, but they do. Quantum, quantum. Related discussion.)

In metals, electrons are not bound to a particular nucleus. Therefore, in a metal object, they move randomly about.

Therefore, they will cross any and all cross sections through said metal object.