Video Transcript
Electrical wires are often made of
a copper core covered in a thin plastic coating. Which of the following are reasons
why copper is chosen as the material for the core of the wire? a) It is a good
thermal conductor. b) It is very cheap. c) It is ductile. d) It is very light. E) It is a good electrical
conductor.
So, this question is focusing on
why exactly we choose copper as the material to make most of our electrical wiring
from. We’ve been given five different
potential reasons, and we need to work out which of these are actual reasons as to
why we use copper. So, let’s go through them one by
one.
Firstly, starting with a), it is a
good thermal conductor. Now, a good thermal conductor
easily allows heat to flow through it. And it’s true that copper is a
pretty good thermal conductor. However, this is not a reason why
we’d select copper. Because when we choose a wire
material, we’re interested in how it conducts electricity, not so much in how it
conducts heat. Strictly speaking then, good
thermal conductivity is not a factor in our choice because the fact that it’s a good
thermal conductor is not really relevant to electrical wires. And so, option a) is not an answer
to our question.
Moving on to option b) then, it is
very cheap. Now, copper is kind of cheap, but
there are other substances that are much cheaper. For example, if we think about
metals, then aluminium is cheaper than copper. And so, it’s not really true that
copper is very cheap. By the way, the reason that we
don’t use aluminium is because aluminium is not as good of an electrical
conductor. Copper is much better at carrying
an electrical current than aluminium is.
Anyway, moving on to option c)
then, it is ductile. Now, this word here ductile refers
to a material, in this case copper, that can be drawn out into a thin wire. In other words, any material that
we can take from being, let’s say, a slab and apply pressure to it in certain
directions to draw it out into a thin long piece of wire without breaking, of
course, is known as a ductile material. And this is a very useful property
of copper because if we want to make long thin wires, then we need a material that
can be turned into long thin wires. And therefore, option c) is one of
the answers that we’re looking for. The fact that copper is ductile is
one of the reasons that we use it to make electrical wiring.
Moving on to option d) then, it is
very light. Now, this is not really true,
either. In fact, for the same amount of
stuff, for the same amount of substance, if we compare copper and aluminium once
again. So, say for example, we take two
cubes of the exact same volume, one is copper, and the other is aluminium, then the
aluminium cube is lighter. Or in other words, we can say that
the density of aluminium, the amount of mass found in every unit of volume, is lower
than the density of copper. And so, it’s not true that copper
is very light.
Therefore, moving on to the final
option, option e) says that copper is a good electrical conductor, which means that
it’s good at carrying an electrical current. And this definitely is true. And it is a reason that we use
copper in order to make electrical wires because we need something that can easily
carry an electrical current. And therefore, at this point, we’ve
gone through all of the options and found our answers. The reasons that we use copper to
make electrical wires is because, firstly it is ductile, and secondly it’s a good
electrical conductor.
