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For example, if this spark gap has a kilovolt of power behind it @ 1A and the other is also at a kilovolt but is @2A will there be a visual difference (i.e. will the one with higher current be thicker, have a different color, etc.)?

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    $\begingroup$ I would expect the intensity of the spark to change with the energy (which you would typically express in Joules as it will be a very large current for a very short time... I don't think you will ever get just one amp in a spark, and what you see is the integral of power over time, i.e. energy). $\endgroup$ – Floris Jun 8 '15 at 15:37
  • $\begingroup$ This question is very relevant to the testing of internal combustion engine ignition systems, as common wisdom ( not necessarily correct ), is that all other factors being constant, a weak, low current spark will appear thin and orange / yellow while a strong current spark will appear thick and blueish / white. However, this is debated, and I've actually asked a question requesting some kind of empirical or theoretical verification of this on the automotive stack exchange: mechanics.stackexchange.com/questions/27366/… $\endgroup$ – Robert S. Barnes Mar 22 '16 at 13:42
  • $\begingroup$ One point of interest is that ( if I understand things correctly ) the power of light is inversely proportional to it's wavelength, meaning blue light is about 40% more powerful than orange light based on the ratio of their wavelengths. So I might conclude from that all other things constant, the blue spark has 40% higher current than the orange spark. $\endgroup$ – Robert S. Barnes Mar 22 '16 at 14:04
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Yes there is. I ran across an automotive site which did such an experiment where they varied spark amperage, while maintaining a constant gap.

In the article, "Understanding, Testing and Calibration of Ignition Coil Dwell Time", the authors used a 5mm spark gap, while documenting the appearance and oscilliscope waveform of a 2 amp spark and a 7 amp spark (qualifiers- inductive ignition, free air test gap):

2 Amps of coil primary current

2 Amps of coil primary current

7 Amps of coil primary current

7 Amps of coil primary current

In the waveforms they recorded, the 2 amp spark lasted 0.5 milliseconds, while the 7 amp spark lasted 1.4 milliseconds.

There may be color differences as well, but I haven't been able to find concrete documentation of this, beyond a little orange in the center of the 7 amp spark above.

EDIT

I spoke with the author of the above article in an e-mail exchange, and he said ( among other things ):

Spark colour in a given gap would mainly be a function of spark current and temperature.

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