I think what you mean is: if you put the same voltage on a wire of each
material, which one let's more current through? The voltage is the
"push" on the electrons, and their flow is the current. If you have a
nichrome wire and a copper wire the same size and shape, with the same
voltage on them, much more current will flow through the copper. We say
that the copper has higher 'conductivity'
or lower 'resistivity'.
The biggest single reason why it's harder for the current to flow
through the nichrome is that it's an alloy of two metals, nickel and
chromium, which are not too similar to each other. Instead of
flowing
smoothly through the material, the electrons frequently bounce off the
unevenness that the mixed-up nickel and chromium atoms make.
You can picture this by thinking of waves travelling in a shallow pond.
If the bottom is even, the wave will travel smoothly. If the bottom is
lumpy, the wave will scatter off in different directions. It sounds
like I'm saying something weird- that to understand how electrons move
in a wire you have to think of them as waves. That really is what I'm
saying!
There are other things too that make nickel and
chromium happen to have more resistivity than copper, even if the
nickel and chromium are separate. But those things also involve
thinking about the electrons as waves, and I've probably said enough
weird stuff for
today.
Mike
(published on 10/22/2007)
