# Question Video: Identifying Charge Separation in a Material Science

The picture shows electrons and atomic nuclei in a piece of material. The electrons cannot flow along the material. The blue circles represent the electrons and the red circles represent the atomic nuclei. At which end of the material is there a build up of electrons. Fill in the blank: The buildup of electrons at one end of the material creates an ＿ along the piece of material. [A] electric current (B) electric potential difference

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### Video Transcript

The picture shows electrons and atomic nuclei in a piece of material. The electrons cannot flow along the material. The blue circles represent the electrons and the red circles represent the atomic nuclei. Part one, at which end of the material is there a build up of electrons. Part two, fill in the blank. The buildup of electrons at one end of the material creates a blank along the piece of material. (a) Electric current, (b) electric potential difference.

We are told that in this picture here, the red circles represent atomic nuclei and the blue circles represent electrons. Our first task is to determine which end of this material has a buildup of electrons. That is, which end of the material has more electrons than the other. Looking at the picture, we can see that there are many more blue circles at the right-hand end of the material than there are at the left-hand end. But since blue circles represent electrons, we can see that there is a build up of electrons at the right-hand end.

To address the second question, recall that a separation of charges creates a potential difference. Looking back at the picture, since there are more electrons than there are nuclei at the right-hand end, there is a net negative charge at this end. And at the left-hand end, there are more nuclei than there are electrons. So there is a net positive charge. So the build up of electrons result in a charge separation, which creates a potential difference. And electric potential difference is the answer that we’re looking for.

We also know that our other choice, electric current, cannot be correct because, as we are told, the electrons cannot flow along this material. And by definition, an electric current is a flow of charges. So since charges cannot flow, electric current cannot be the correct answer.