30. Dissectable Leyden Jar

This is a very impressive demonstration which will draw lots of comment! It can be used to emphasize the difference between conductors and insulators.

The dissectable Leyden jar is charged up with a Van de Graaff and then discharged by shorting the inner and outer can to show charge storage. Then the jar is recharged and disconnected from the Van de Graaff. The inner can is lifted out with an insulated tool, or, with care, by hand. At this point the parts of the jar are safe to handle, and the glass jar can be lifted out, the inner and outer cans touched to each other, or touched to the glass jar in any combination. You can even give the pieces to the students to handle.

When the Leyden jar is reassembled, the last step of inserting the inner can being done carefully, it will be found that the jar is still charged, as can be checked by shorting its terminals and drawing a spark.

The discovery of the Leyden jar as described in a letter written by Musschenbroeck to Reaumur in 1746.

"I wish to inform you of a new, but terrible experiment, which I advise you on no account personally to attempt. I am engaged in a research to determine the strength of electricity. With this object I had suspended by two blue silk threads, a gun barrel, which received electricity by communication from a glass globe which was turned rapidly on its axis by one operator, while another pressed his hands against it. From the opposite end of the gun barrel hung a brass wire, the end of which entered a glass jar, which was partly full of water. This jar I held in my right hand, while with my left I attempted to draw sparks from the gun barrel. Suddenly I received in my right hand a shock of such violence that my whole body was shaken as by a lightning stroke. The vessel, although of glass, was not broken, nor was the hand displaced by commotion: but the arm and body were affected in a manner more terrible than I can express. In a word, I believed that I was done for."