Safety.
The leads limit the current.

The old safety adage
"it's the volts that jolts but it's the mils that kills"
applies.

The carbon is a resistive conductor.
Brilliant idea on the part of the seller.

edit: studiot beat me to it.

I obviously came to the right place. This explains why, no matter how close I put the probes together when measuring the resistance of the fibers, I would read approx. 25 ohms.

Thanks, everyone!

 

First experiment: I separated the fibers and found that the black ones are conductive and the white ones aren't.

Second experiment: No longer having the chemistry set from my childhood, I performed the most obvious, chemical experiment on the mysterious fibers. I put a lighter to them! The white ones melted into a nice, plastic blob. The black ones glowed red hot, but did not burn at all. In fact, they appear totally unscathed.


I believe you are correct. And I'm thinking the black ones are pure carbon.

.

Caustic soda (drain cleaner) usually makes carbon disappear as if by magic.

I remember someone trying to decoke an aluminium cylinder head in caustic - the carbon vanished, but so did the cylinder head!

 

 

When I started to read this I figured it would be Litz wire http://en.wikipedia.org/wiki/Litz_wire
But it turns out it isn't..

 

When I started to read this I figured it would be Litz wire http://en.wikipedia.org/wiki/Litz_wire
But it turns out it isn't..

Litz is just like stranded wire except the strands are enamelled - all the Litz I've seen had a woven fabric outer covering.

 

Litz is just like stranded wire except the strands are enamelled - all the Litz I've seen had a woven fabric outer covering.

The Litz I'm familiar with is twisted with some sort of thread, mostly seen in older headphone sets. Not sure about the "enameled "part though.

 

The Litz I'm familiar with is twisted with some sort of thread, mostly seen in older headphone sets. Not sure about the "enameled "part though.

Litz is for high frequency work - as frequency increases, the "skin effect" becomes dominant, that means the current repels itself so it only occupies a "skin" - a shallow depth on the surface of the conductor. Individual strands in Litz wire are insulated from each other so they don't just become the same as a solid mass. The best Litz wire has the greatest number of the thinnest possible strands - it would be seriously expensive to fabric cover each strand!!!

In valve era headphone leads, you wouldn't mind them being pretty lossy for RF, detectors were generally a pretty simple affair, and RF suppression was usually just a shunt capacitor somewhere between the detector and phones.