How much of the video (post #2) did you watch? The explanation comes about 11 minutes after the introduction to the Leyden jar at about 27 minutes in.

... but the way I see it is that electrons inside the jar, repel electrons on the outside of the jar (as long as there is an earth path to allow the electrons to move away from the jar), leaving an opposite positive charge.

 

So can you please explain how this happens?

Yes, indeed the video explained perfectly.

They showed the jar being stood on an insulator and clearly said no significant charging was effected.

They then went on to say that one day, by mistake, the insulating pad was omitted and the jar hand held.
The jar was then rapidly charged.

Since a human is not an insulator the human provided a path to ground. And the outer metal draws its chage from ground.

I can only say again, watch the video.

 

thats right, if you charge a capacitor with only one lead connected it dont work. it requires both connections, layden jars anre not some kind of magic, they are an early form of capacitor. works by having a charge diffeence between two conductive plates. in the old days they said that the "electric fluid would fill the jar" Tesla even used jars for capacitors, in Colorado, he used bottles filled with salt water sitting in a tub also fille with salt water. the glass was the insulator, and the salt water made the conductors.

 

Hi, Davebee, can I please get your feedback on this post? (Is there a way for me to send messages to you directly?)

In three different videos, it is stated explicitly that the Leyden Jar works due to the outside conductor being grounded, so I'm taking that as an assumption.

Here then is my summary of how the Leyden Jar works:

A glass jar has a metal lining inside it and a coating outside it, thus the metals are separated by the glass, which is an insulator. A metal conductor is inserted into the jar so that it is in contact with the inner metal at one end and sticks out the top at the other end.
1. A charged object is brought in contact with the metal conductor. This charges the metal lining inside the jar, giving it the same charge as the charged object.
2. As a result, the metal coating outside the jar becomes polarized: the surface nearest the jar takes on a charge opposite to that of the inner metal lining, and the outside surface of the metal coating outside the jar takes on a charge equal to that of the inner metal lining.
3. If the outer metal coating is grounded, then the charge of the outer surface of the metal coating outside the jar will become neutralized, and the metal coating will now be left with a net charge opposite to that of the metal lining inside the jar.
4. Steps 1-3 can be repeated many times, so that quite a bit of charge can be stored up.
5. If you then connect by a conductor the outer metal coating with the metal conductor attached to the inner metal lining of the jar, giving a path from the one to the other, then electrostatic discharge will occur, and a shock will be observed.

The following is how the explanation from the video referred to in this thread:

As the jar is charged up, negative electrical charge is poured down the wire and into the water. If the jar rests on an insulator, a small amount builds up in the water. But if instead the jar is held by someone as it's being charged, positive electric charge is sucked up through their body from the ground to the outside of the jar, trying to cancel out the negative charge inside. But the positive and negative charges are stopped from cancelling out by the glass, which acts as an insulator, so instead, the charge just grows and grows.

Does this explanation differ from mine? My explanation relies on polarization as the mechanism through which the outer metal is charged, whereas this explanation makes no mention of polarization.

 

If you understand and follow these simple rules it is easy.

Dielectrics become polarised, not conductors.

Charges move through conductors, not dielectrics.

1. A charged object is brought in contact with the metal conductor. This charges the metal lining inside the jar, giving it the same charge as the charged object.

Charges move through conductors, not dielectrics.

Not the same charge.
The distribution of the charge in the charged body extends to include the connected conductive parts of the jar ie the metal inside.

2. As a result, the metal coating outside the jar becomes polarized: the surface nearest the jar takes on a charge opposite to that of the inner metal lining, and the outside surface of the metal coating outside the jar takes on a charge equal to that of the inner metal lining.

Dielectrics become polarised, not conductors.

3. If the outer metal coating is grounded, then the charge of the outer surface of the metal coating outside the jar will become neutralized, and the metal coating will now be left with a net charge opposite to that of the metal lining inside the jar.

If a charge is neutralised how can that result in a net charge?

5. If you then connect by a conductor the outer metal coating with the metal conductor attached to the inner metal lining of the jar, giving a path from the one to the other, then electrostatic discharge will occur, and a shock will be observed

If you conncect via a conductor, a current will flow, discharging the Leyden Jar and you will likely observe nothing.

The electrostatic discharge (spark) occurs when you nearly make a connection ie leave a small gap, and the spark is observed to jump across the gap. You feel a shock if you form part of that nearly complete conductive path whether it is complete or nearly complete.

 

Studiot, you state that conductors cannot become polarized, but isn't polarization of a conductor the very basis of the operation of an electrophorus?

https://en.wikipedia.org/wiki/Electrophorus

I'm suggesting that the outer conducting surface of a Leyden jar may be acting just like the metal plate of an electrophorus.

Superconductor, I'd rather keep the discussion in this thread so others can check what we say, learn from us when we're right and give us feedback when we're wrong.

 

Studiot, you state that conductors cannot become polarized, but isn't polarization of a conductor the very basis of the operation of an electrophorus?

https://en.wikipedia.org/wiki/Electrophorus

I'm suggesting that the outer conducting surface of a Leyden jar may be acting just like the metal plate of an electrophorus.

It's charge separation not polarization in the metal plate of the electrophorus and the Leyden jar. There is a difference. How can you polarize the free electrons of the same type charge in a conductor?

 

Here's another website that uses the term polarization the same way I did.

http://www.physicsclassroom.com/Class/estatics/u8l1e.cfm

You're saying that polarization is not the right term for this case - what's your source of that definition?

 

You're saying that polarization is not the right term for this case - what's your source of that definition?

I guess it's more like a cause and effect. Separation is the cause of the electric field and movement of charge to opposite ends of the conductor by the external field to keep it neutral so at this point we could say it's polarized by charge separation. As the conductor remains neutral overall, removal of the external field also removes the separation/polarization in the conductor unless we have a circuit for charge from one side to move to ground while the external field is applied like in the electrophorus metal plate with your finger.

 

"I spent about 30 minutes reading on capacitors, and even then, I'm not sure what the answer is."




Not enough time.

After studying for over 1 year, and I still get stumped, every now and then.

 

I really liked the explanations given here:

https://www.youtube.com/watch?v=3bQYsJP2R3Y

Leydon jar is covered at about 16 minutes in, but I recommend you watch the whole program

I really wanted to watch that, but the account was deleted.....

 

Superconductor, I'd rather keep the discussion in this thread so others can check what we say, learn from us when we're right and give us feedback when we're wrong.

No problem. Can I please ask that you read that last post of mine #24 and tell me whether you agree with my summary there? (As well as see the question which I ask at the end of that post.)

 

Davebee

Studiot, you state that conductors cannot become polarized, but isn't polarization of a conductor the very basis of the operation of an electrophorus?

Davebee it is always good to discourse with you since take an opposite view in such a polite manner.

As this question and answer below correctly notes there are many meanings to the word polarization(US) or polarisation(UK). My science dictionary has 5 and I can think of yet more.
Unfortunately, after noting an unusual one to do with leads and connectors, the author rambles off and wrongly states entirely the opposite view to the one I put forward.

https://uk.answers.yahoo.com/question/index?qid=20110226073428AAyTePw

Q: Is polarization for insulators or conductors, or both?

A : The meaning of the question is not very clear but I will try. "polarization" has many meanings; see it in Wikipedia.................

Dave your link makes some excellent points, inlcuding this one:

Polarization is Not Charging
Perhaps the biggest misconception that pertains to polarization is the belief that polarization involves the charging of an object. Polarization is not charging! When an object becomes

Now we are discussing polarisation in the context of the Leyden Jar, not in the imposed electric field of a polarised object.

'Polarization is not charging' and the Leyden Jar uses charges and charging.

This animation makes clear the difference. Note there are only charges of one polarity in play in the conductor. It is not polarised.

http://www.regentsprep.org/Regents/physics/phys03/ainsvscon/

See also slide 15 from Texas University

www.ph.utexas.edu/~phy303l/lectures/Week3/15.4-15.8.pptx

Again, Dave's link takes one of the main heads of meaning of the word polarisation, notably that of separation, and develops its discussion from there.

Another head of meaning, hugely relevent to dielectrics, is that of orientation. As in the orientation of a dipole or wave relative to an electric field.

That is developed here

http://electrons.wikidot.com/polarization-of-ceramic-materials

Note also that Chemists use two additional meanings of the word in electrochemistry - relevent to battery technology, electrolysis etc.

That is also in the TexasU slides.

Finally electric curent can flow by one of three means

Conduction
Convection
Displacement

And polarisation, P, is defined in Maxwellian electric theory as a particular vector.

I was trying to simplify before.

 

an awfull lot of discussion about a simple capacitor.

 

an awfull lot of discussion about a simple capacitor.

If they were simple at the physics level we won't need to have this discussion. Because this is physics instead of electronics it's good to dig down deeper because capacitance is a measure of charge and charge is the fundamental property of matter that gives rise to the electromagnetic force interaction between particles.

 

the charge between the two plates puts a strain on the dielectric (glass jar) at least untill it braks down the insulation. the glass and its impurities detremine the dielectric constant, and the thickness of the glass determines the breakdown voltage. the area of the plates and the dielectric constant determine the capacitance (amount of storeage)
something real interesting would be why the same materials that increase dielectric constant in glass also increase refractive index.

 

the charge between the two plates puts a strain on the dielectric (glass jar) at least untill it braks down the insulation. the glass and its impurities detremine the dielectric constant, and the thickness of the glass determines the breakdown voltage. the area of the plates and the dielectric constant determine the capacitance (amount of storeage)
something real interesting would be why the same materials that increase dielectric constant in glass also increase refractive index.

This is all true, but how is it relevent to the operation of a Leyden Jar?

After all, my chair is subject to stress and strain when I sit on it, but I do not need a learned discussion in the mechanics of materials to know where to park my _ss.

 

because a leyden jar is nothing but a capacitor. trwo conductors seperated by an insulator.

 

Do you normally charge your capacitors from a friction generator?

 

I can, I have several very high voltage rated capacitors.