Video Transcript
Complete the following
sentence. When a wire has an electric current
in it, blank are moving along the wire. (A) Electrons, (B) atoms, (C) the
nuclei of atoms.
An electric current is the flow of
charged particles. This question is asking us to
identify which charged particles flow when there is a current in a wire.
Recall that a wire is made up of a
very large number of atoms. We can draw an atom like this. Each atom consists of a nucleus and
one or more electrons. An electron has a negative charge,
and the nucleus has a positive charge. It is important to remember that
the nuclei of atoms do not move around the wire. They always stay in the same
place. So option (C) is not the correct
answer.
If the nucleus of an atom does not
move, then that means that the atom itself doesn’t move either. Option (B) is not the correct
answer.
That leaves us with only one
possible answer, (A) electrons. The electrons in a wire are able to
move around, meaning that a current can flow in the wire. Let’s think about why electrons
flow around the circuit. A particle’s charge determines how
it will interact with other charged particles. Recall that particles with unlike
charges, a positive charge and a negative charge, attract. There is a force between the
negative and the positive charges that pulls them towards each other. On the other hand, particles with
like charges, such as two negative electrons, repel each other. The force between them pushes them
apart.
There can be a current in a wire
when the wire is connected to a cell. A cell has a positively charged
terminal and a negatively charged terminal. The electrons in the wire are
repelled from the negative terminal of the cell and attracted to the positive
terminal of the cell. Because electrons are able to move,
this causes the electrons to flow around the circuit.
So, when a wire has an electric
current in it, electrons are moving along the wire. The correct answer is option
(A).
