MIT Physics Demo -- Dissectible Capacitor

Leyden Jars, an early style of capacitor, can be connected to the two electrodes of the Wimshurst Machine. They will store charge as it is generated, giving a much stronger spark across the gap.

Next we have a three-piece dissectible Leyden Jar consisting of two metal cups separated by a glass cup. When charged with the Wimshurst machine, we see by touching it with the shorting rod that it holds a large amount of charge. However, when disassembled, the metal cups can be brought into contact with each other and no spark will be generated. When the jar is reassembled it can then be discharged. This demonstrates that, in this situation, the charge actually resides on the surface of the glass (a dielectric), not on the metal.

See the original video an more on MIT TechTV here - http://techtv.mit.edu/videos/1698-dissectible-capacitor

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[atelierrobin]

It cannot be misleading if it shows a real phenomena.

No misconceptions here. If we would would never investigate "Odd" behaviors, there would be no science and we would still be swapping pebbles in unheated caves.

[frapente]

Amazing.

After years of theory and mathematical formulas,I never actually understood  how a capacitor works and why it stores energy inside itself.Copper plates have'nt charge...charge is inside glass...is it true?

I'm astonished to see you can put togheter copper plates without discharge,and then if you reassemble the structure,energy discharge happens.

Energy seems vanish...where is it gone?

What really happens inside glass when gear works?

I don't understood very well.

[PoirierMike]

Impressive coming from MIT ! ;)

[brahmabullsj]

The illusion from the demonstration, "energy" is stored within the glass. However, I don't believe the real answer is so simply. Space itself (e.g., pure vacuum) may also be used as dielectric.  What is the behavior in this situation? 1) is the charge localized to the space, 2) charge is retained on metal. #1 would seem to be a strange behavior since implies absolute position. #2 is a departure from the original demonstrated behavior. I am interested to know if someone knows the answer.

[rastarockerzz]

@SIMKINETICS

simply because the point where he is picking up the jar is neutral U(electric potential)=Vm-Vn=L/q. We are talking about an dielectric a non conductive material that will charge up only on the area where the charge Vm and Vn are inducted by copper. If you are looking carefully he is touching the area where the copper armature's weren't charge inductive so the Vm and Vn on that area = to almost 0 coulombs If U= Vm-Vn then U = almost 0 Volts.

[GreenLearning]

Wow! How to balance this with the MIT demo where the voltage goes WAY WAY up when capacitor plates are separated... This really intrigues me!

[mikepousti]

great invention.. Appreciate the thoughts.



[SIMKINETICS]

@rastarockerzz When he picks up the pyrex beaker, why doesn't the charge conduct to his hand?

[coldarc]

the glass holds an electric field. when the electric field is separated between plates of unequal influence one plate gain more negative charge than the other, the difference between them create voltage.

[rockerzac99]

i think you made a Magnetto

[HoneycombAgent]

Where does the electrical charge go?