Walter Lewin's Riddle at 37:00: The Surprising Conductor Plate Spark Explanation

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Discussion Overview

The discussion revolves around a riddle presented by Walter Lewin regarding the behavior of a charged conductor with a dielectric inside. Participants explore the phenomenon of a spark occurring when the conductor plates are reconnected after being discharged and removed, questioning the underlying reasons for this occurrence.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant suggests that the spark may be due to the dielectric remaining polarized when the plates are reinserted, potentially causing the plates to become charged by induction.
  • Another participant proposes a mathematical approach by referencing a simpler case of a plane capacitor with a dielectric, encouraging calculations of the electric field and potential difference to understand the conditions for sparking.
  • A participant expresses curiosity about how Walter Lewin discovered this phenomenon.
  • One participant shares enthusiasm for Walter Lewin's explanations and teaching style.

Areas of Agreement / Disagreement

There is no consensus on the exact reason for the spark; participants are exploring different hypotheses and approaches without resolving the question.

Contextual Notes

The discussion involves assumptions about the behavior of dielectrics and electric fields, and the calculations suggested depend on specific conditions that are not fully detailed in the posts.

Who May Find This Useful

Readers interested in electrostatics, dielectrics, and the educational methods of Walter Lewin may find this discussion engaging.

Nikitin
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At 37:00 he charges a conductor with a dielectric inside, removes the conductor plates and discharges them, and in the end puts them back into position.

Then something "remarkable" happens - when he connects the conductor plates with each-other, a spark is produced. Why did this happen?

------------

Is this because the dielectric is still polarized when he puts back the plates, and thus the plates themselves become charged (by induction) in turn? If not, what is the answer to this riddle?
 
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You're on the right track. If you want to put some math on it, consider the simpler case of a plane capacitor, with a dielectric and two gaps. Calculate the field both in the gaps and in the dielectric needed to have a potential difference around 20kV between the two plates, and compare to the breakdown field for air (around 3MV/m)
 
How did he discover this?
 
This is marvelous! I could listen to this guy the whole day :-)).
 

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