Electrons cannot sense electrostatic force?

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Discussion Overview

The discussion revolves around the behavior of electrons in circuits, particularly in relation to measuring voltage and current with a multimeter when connected to a DC power supply or charged capacitor. Participants explore the differences between steady-state (DC) and changing conditions (AC), and the implications for measurement techniques and device responses.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions why there is no voltage or current detected when connecting a multimeter to a DC power supply or charged capacitor, suggesting that electrons cannot sense the bulk of electrons present.
  • Another participant explains that multimeters require current flow and that the scenario described involves an open circuit with zero current.
  • A participant points out that antennas, which can also be considered open circuits, do exhibit current flow, indicating a potential inconsistency in understanding the behavior of different circuit types.
  • There is a discussion about the differences between steady-state (DC) and changing conditions (AC), with an emphasis on the complexity of electromagnetic phenomena.
  • One participant suggests that the lack of detection by a digital multimeter (DMM) could be due to its sampling method, which averages over time, potentially missing short-duration events.
  • Another participant proposes that using a digital storage oscilloscope (DSO) might yield better results due to its higher sample rate, allowing for the detection of shorter time periods.
  • There is a mention of the relevance of series resistance and the RC time constant in determining the visibility of pulses in measurements.
  • Participants note the importance of energy (area under the curve) in making pulses visually detectable, rather than just time constants alone.
  • One participant highlights the lack of a circuit diagram, which complicates the discussion and understanding of the specific situation being analyzed.

Areas of Agreement / Disagreement

Participants express differing views on the behavior of electrons in circuits and the effectiveness of measurement devices under various conditions. There is no consensus on the underlying reasons for the observed phenomena, and multiple competing explanations are presented.

Contextual Notes

The discussion includes assumptions about circuit configurations and measurement techniques that are not fully detailed, which may affect the interpretations of the participants. The lack of a circuit diagram limits clarity on the specific conditions being discussed.

thomasj
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Why there is not voltage or current just for 1ms if I connect a multimeter ground to the negative terminal of a DC power supply or charged capacitor? Why electrons in measure lead and DMM device cannot sense a bulk of electrons (or lack of it)? I tried with an 5kV DC power supply too. In an antenna they sense this force and move from or to the source.
 
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thomasj said:
Why there is not voltage or current just for 1ms if I connect a multimeter ground to the negative terminal of a DC power supply or charged capacitor?
Because multimeters work on current flow and you are talking about an open circuit with zero current flow.
 
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phinds said:
Because multimeters work on current flow and you are talking about an open circuit with zero current flow.
But an antenna also an open circuit and there is current in it.
 
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thomasj said:
But an antenna also an open circuit and there is current in it.
This is a good observation and shows the danger of confusing steady state conditions (DC) with changing ones (AC /Step Functions / Pulses). EM can't be dealt with with simple, one-line statements. Even JC Maxwell needed Three Equations!
 
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sophiecentaur said:
This is a good observation and shows the danger of confusing steady state conditions (DC) with changing ones (AC /Step Functions / Pulses).
Interesting but can you explain, please? I tried to use pulse DC with a push button but no effect.
 
thomasj said:
Interesting but can you explain, please? I tried to use pulse DC with a push button but no effect.
The title of your thread refers to Electrostatic Forces. When the forces are not Static, things are different. The reason that your DMM recorded nothing will be a combination of factors. Firstly, a Digital Analogue Converter (the heart of a DMM) takes samples and gets an average over its sample interval. The total charge that passes with an experiment like yours will depend on the Capacitance of the apparatus. The peak current could be fairly high (easily detectable by your DMM) but the average may be very small. It's the sort of thing that a 'clunky' analogue meter might show you by a tiny twitch of a needle. (Newer doesn't always mean better. :wink:)
 
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sophiecentaur said:
... but the average may be very small. It's the sort of thing that a 'clunky' analogue meter might show you by a tiny twitch of a needle. (Newer doesn't always mean better. :wink:)
Thanks, I suspect this. And if I would use a DSO instead? Sample rate of that device is high enough I guess. Shorter time period's average could be better here.
 
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thomasj said:
nd if I would use a DSO instead? Sample rate of that device is high enough I guess.
Depending on the capacitance of that wire, picoseconds or nanoseconds might be needed to see the spike.
 
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anorlunda said:
Depending on the capacitance of that wire, picoseconds or nanoseconds might be needed to see the spike.
The series R would be relevant, wouldn't it? RC time constant would be longer
 
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sophiecentaur said:
The series R would be relevant, wouldn't it? RC time constant would be longer
The way the OP stated it, is is the R of a short piece of wire.

But time constant alone does not make it visible. It is area under the curve, i.e. energy, that makes the difference between visually visible or invisible pulses.
 
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anorlunda said:
The way the OP stated it, is is the R of a short piece of wire.

Again, there is no circuit diagram to enable us all to be discussing the same situation. I assumed that a meter was in series.
 

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