It isn't clear if you were still discussing piezoelectric igniters, or if you had changed the subject.
Your concerns are valid for systems with appreciable current (say half a milliampere), but are not so much a concern with piezoelectric igniters. I often test my igniters by making the spark jump from or to my finger.
Let's say the power produced by a piezoelectric igniter is in the range of half a microwatt.
The current is thus 0.03 nanoamperes.
At currents like this, there is no appreciable heating of a carbon composite resistor, and the resistors are long enough that the spark does not arc around from lead wire to lead wire. So you can pretty much ignore voltage ratings.
If the cuvette is really 40,000 ohms, then we might have a problem, as the voltage drop across that gives you 0.8 microvolts. You might want to simply place two wires very close to one another inside the cuvette (or Petri dish -- we don't need the cuvette anymore) and hit the igniter a couple dozen times.
On Wed, Jul 30, 2014 at 2:51 PM, Tom Knight <tk@ginkgobioworks.com> wrote:
Most carbon composition resistors have a voltage rating of 500 volts. You need a set in series to keep the voltage rating under control. The typical time constants for electroporation are in the 3-7 millisecond range. High voltage capacitors can kill you. Make sure you have bleeder resistors across them. They also have a memory, so even if you discharge them, they can spontaneously charge again.
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