Capacitor+Grounded Plate+AC Current?

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The discussion centers on the phenomenon observed during a physics demonstration where a pickle ignites when connected to an AC outlet. Participants debate the reasons why the fire consistently starts at the end connected to the "hot" terminal, despite the alternating nature of the current. Key insights include the role of the pickle as a resistive load and the impact of current density at the point of contact, which leads to localized heating. The conversation also touches on the implications of grounding and the behavior of electrical energy flow in resistive elements.

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  • Understanding of AC current behavior and its effects on resistive loads
  • Knowledge of electrical circuits, including hot and neutral connections
  • Familiarity with concepts of current density and thermal dissipation in conductors
  • Basic principles of electromagnetism and energy flow in circuits
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  • Research the principles of AC circuits and their effects on resistive loads
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Physics students, electrical engineers, educators demonstrating electrical concepts, and anyone interested in the practical applications of AC current in resistive materials.

  • #31
A clue to the operating principle of the pickle light emitter might be found by examining why its emission eventually ceases; the lighted region seems to jump about and emission starts and ends as suddenly as though a switch were thrown, and this is not consistent with the glow emitted due to a sizeable body being heated to incandescence. In fact, a consensus among writers is that the light is the sodium spectrum, and arises from the high salt content in the pickled cucumber.
 
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  • #32
There is no doubt that the glow is not heat glow. Did you read the paper I linked to? It is proposed there is plasma arcing within the pickle.
I think it is plausible that the side of the pickle to actually burn first would be the same side that first glows. I've seen the small side glow, and the fat side glow. I have no theory founded in electronic or physics theory (such as the proposed idea that the energy flow in an AC circuit has a "direction" because of the difference between neutral and ground) that would support the professors claim that "the same side always burns first".
 
  • #33
I agree with those who say it is the order of connection, or the resistance right at the point of connection. It cannot be anything else. The big problem is why the resistance would be lower at one connection point. It may be that something is distributing the connection at the grounded neutral or "cold" terminal causing a larger cross sectional area (and less resistance) for that termination, or something is concentrating current in a smaller cross sectional area at the "hot" terminal causing the same current through a smaller area (more I^2 R heating from more resistance around that termination). It cannot be anything else.

This reminds me of a clock. My 120V electric motor ship clock was subjected to a lightning surge that shorted near one end of the winding to the motor frame. This made it sensitive to stray capacitance or leakage to ground. If I installed the plug one way, it ran forward. If I installed the line plug the other way, it ran backwards. I had an unbelievable amount of fun with that clock, until I discovered the clock face was at 90 volts or 30 volts to ground, depending on insertion. The pickle, however, cannot be like the clock because impedance levels are far different. It cannot be sensitive to displacement currents via capacitance like the high impedance clock motor.
 

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