To expand on that for the electron-challenged, an inductor is effectively a frequency dependent resistor. The higher the frequency, the higher the resistance. So, the fundamental pulse to the plug makes it through (though slowed slightly), while the harmonics (noise) that were generated  can't get past the extra resistance presented to them.

The reverse is true for a capacitor. That's one of the reasons why you see capacitors with one leg tied to the power supply & the other to ground. The capacitor blocks DC but passes higher frequencies (the noise) to ground.

I have no doubt that the above will make physicists cringe, but it's close enough to working knowledge for us builders to use.

Charlie

On 07/09/2011 08:28 AM, Tracy wrote:

In this case "shielded" is the wrong term.   The spiral wire does not actually shield the noise, it prevents the noise from being transmitted.    It acts as an inductor to prevent the propagation of the noise generated at the spark gap from propagating up the wire.

Tracy

Sent from my iPad

On Jul 9, 2011, at 2:09 AM, Lehanover@aol.com wrote:

It has to do with the resistance of the long thin Monel wire. An impedance mismatch and inductive reactance. What the mechanism is I do not know. That is why Tracy is here, to explain such matters.

 

Lynn E. Hanover

 

In a message dated 7/8/2011 11:08:09 P.M. Paraguay Standard Time, SBoese@uwyo.edu writes:

My last massage got a little garbled, the way I have my wires configured now, the conductor and spiral wrap are exposed and folded under the crimped teminal ends, so aren't both the conductor and the spiral wrap acting as a conductor? What is doing the shielding?

 

Brian Trubee