Lead Layden Jars

[john_g]

I noticed that quite a few of the very old layden jars used lead as the charge plates rather than aluminium. Lead has a higher ammount of electrons per surface area than aluminium, so does this make it a better choice of material?

Also why were small chains used to carry the charge from the inner plates to the "jar Top" rather than a solid conductor?

Any thoughts much appricated.

Regards
John

[lookingin]

Lead Layden

In a letter to Thomas Hubbard in Boston, dated 28 April, 1758, Franklin describes a battery which he is sending to Harvard. A mahogany case lined with lead, containing thirty-five square glass bottles, in five rows, seven in a row. Later in the letter he continues: The middle of the wire goes up into the stopper, with an eye, through which the long communicating wires pass, that connect all the bottles in one row. To form occasional communications with more rows, there must be, on the long wires of the second and fourth rows, four other movable wires, which I call cross-wires, about two inches and a half long, with a small ball of any metal about the size of a pistol-bullet at each end. The ball of one end is to have a hole through the middle, so that it may be slipped on the long wire; and one of these cross-wires is to be placed between the third and fourth bottles of the row at each end; and on each of the above-mentioned rows, that is, two to each row, they must be made to turn easy on the wires, so that when you would charge only the middle row, you turn tow of them back on the first, and tow on the fifth row, then the middle row will be unconnected with the others. When you would charge more rows, you turn them forwards or backwards, so as to have the
communication completed with just the number of rows you want. The brass handles of the case communicate with the outside of the bottles, when you wish to make the electrical circuit.

[john_g]

Lookingin

Thanks for the reply. Do you know if each of the square bottles were lined? or can you post the full letter? Good tip about using any metal for the balls - I have given up trying to find cheap brass ball, maybe I will cast some balls out of lead.

Regards

John

[Inquorate]

Balls of lead

Try using sinkers, for fishing :-)

[Electrotek]

A chain conductor breaks the current up into high frequency micro pulses. This is more compatable than wire with static electricity which has a discharge frequency around 100 kps.

[lookingin]

Just Google--->Franklin lead line leyden

Franklin Explains the Leyden Jar

The Leyden jar is variously called a condenser or capacitor, and the reasons for those two names become obvious when one understands the logic of its operation. The earliest Leyden jars of the mid-eighteenth century consisted of a glass bottle fitted with a cork and filled with water. A copper wire, which was immersed in the water, ran through the cork and was held to a machine generating (let us say) negative charge. Today, we know that this means the generator is sending electrons flowing through the wire and the water, creating a negative charge on the inside of the glass. If the bottle were insulated from the earth, one would soon reach a point at which no more negative charge or electrons could be absorbed by the jar. But with an experimenter holding the outside of the bottle, the results were quite different. Since like charges repel, the force of the negative charges on the inside of the bottle would push electrons out from the experimenter's palm and the adjacent glass and ultimately into the earth. The positive charge remaining on the experimenter's hand and adjacent glass would pull on the electrons inside the glass, packing them together more tightly and making room for still more electrons and a greater negative charge. Because the Leyden jar worked by squeezing the electrons or negative charge more closely together, this type of device later came to be called a condenser. (The term seems to have originated with Alessandro Volta in approximately 1780). Because the result of the process was an increase in the jar's capacity to absorb charge, the more modern term for such a device is a capacitor

But even without understanding how the Leyden jar worked, several improvements were made to it. Rather than using the glass itself as both the bearer of charge and the insulator between the two types of charge, William Watson lined the glass jar inside and out with metal foil; the glass then served principally as an insulator. The copper wire through which charge was entering was attached directly to the foil by a metal wire rather than by water.

In a letter of April 1748, "Franklin described some new experiments showing that a charged Leyden jar always has charges of opposite signs on the two conductors and that the charges are of the same magnitude." (I.B. Cohen, "Franklin," The Dictionary of Scientific Biography, p. 131) In that sense, Franklin said, experimenters did not "charge" and "discharge" the Leyden jar. It contained a certain amount of electrical fluid before "charging" and an equal amount afterward. "Charging" the jar simply meant redistributing the fluid, and "discharging" was required because the original equilibrium could not be restored by having electrical fluid pass through the bottle (nor, practically speaking, over the lip of the bottle). It could be restored only through a conducting connection between the outside and inside.

Using an early type of Leyden jar, without foil lining, Franklin then announced the most surprising discovery of all. "The whole force of the bottle, and power of giving a shock, is in the GLASS ITSELF." Franklin proved this by eliminating all the other candidates.

First, he set his Leyden jar on a glass insulator. After he had carefully removed the cork and wire, the jar could still be discharged by having the experimenter touch the outside and the water. Next, he carefully poured off the water from a charged Leyden jar into an empty uncharged jar resting on glass. This jar gave no indication of having received a power to shock. He then refilled the empty Leyden jar with an equal amount of pure water, and discovered that the jar retained the power to shock. Clearly, the glass itself must be implicated.

For a final experiment with Leyden jars, Franklin asked whether the charge on the jar was influenced by shape. This was not so absurd as it may seem. Franklin's first discovery, remember, had been that the shape of conductors had an effect on their ability to discharge an electrified body. So the question about the shape of the jar was hardly silly. To answer the question, Franklin constructed a condensor consisting of two lead plates separated by a flat sheet of glass. It produced the same effect as Leyden jar. Franklin then made a series of eleven such flat condensers and linked up the lead plates with a wire, creating what he was the first to called an "electrical-battery."