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.