Why is there resistance in wires, and when you vary things like the length of the wire, why does the resistance change?
Asked by: Rachel
The best way to answer this is through an analogy.
Imagine the charge that is flowing through a wire
to be water flowing through a pipe. The Rate at
which the water is flowing is the current in an
electrical system, how fast are the electrons moving.
Resistance is what restricts the movement of the
charge through the wire. The length of a pipe,
the cross-section, and the imperfections in the
pipe (clogs and such) all impede the flow of the water,
and are analogous to how electric current is impaired
as it flows through a wire. Things like making the
wire longer and thinner make the resistance go up
since it is harder to push charge through the wire.
So you can see that resistance is inherent in every
type of wire. There are cases when some materials
can be cooled down to very temperatures where they
have effectively zero resistance, but in everyday encounters
electricity this, effect doesn't really have much bearing.
Answered by: Mike Perkins, Physics/Astronomy Major, Penn State
The reason for resistance in wire is because of the composition of the atoms
such as copper, aluminum, of which a particular wire is made of
and the arrangement of the atoms of these metals. When an electron passes through
the wire, the electrons hit these atoms while making the journey from one end to the
other giving opposition or resistance to the electrons. When this happens electrons move an
electromotive force such as voltage, and in hitting these atoms, also creates heat via friction
of the electrons and atoms. When the wire is lengthen, the journey is considerably longer and the
resistance changes. Also, the size of the wire changes the amount of resistance. That is one reason
you don't use a #22 gage lamp cord extension to supply extended power to an appliance of heavy duty. You don't
have the capacity to supply enough electrons efficient enough to run the appliance.
Answered by: Joseph Toy, M.S.
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