Becky Salisbury

The Leyden jar was a device invented in Pieter van Musschenbroek in 1745 that was used for storing electric charge. It was one of the earliest inventions used for experiments in electricity. In respect to the design of the Leyden jar, the outer plate was grounded whereas the inner and outer surfaces of the jar stored equal but opposite charges. Benjamin Franklin was actually studying the Leyden jar, and was the first to realize that the charge was actually stored in the glass and not the water inside the jar. The storage ability or capacitance of the Leyden jar is about 1 farad, an SI measuring unit of capacitance. This great invention was one of the first inventions which helped scientist study static electricity.

Question 63

Although there were several devices used in the seventeenth and eighteenth centuries to study static electricity, the two most well known were the Leyden jar and the Wimshurst machine. The quest for more knowledge involving static electricity was a theme of these two centuries. First off, the Leyden jar was discovered, accidently, by a Dutch physicist by the name of Pieter van Musschenbroek in 1745. The Leyden jar contained an electrode located at the top that was then connected with some kind of conductor to the inner surface of a glass jar. The charges on the inside and outside differ with whether or not they are positive or negative, but in any case there is an equal amount of them. At first water was used in the inside to be created as a means of travel for the condcutor, but later it was discovered that wrapping the glass with metal foil was a better method.

The Wimshurst machine creates static electric sparks when cranked. It is made of two plastic discs, each with spaced out metal sectors. This machine has to supporters on either side and contains a hand wheel used to crank and operate this piece of science equiptment. It also comes with induced charge collecting enablers and Leyden jar capacitators to help maximize its static electric sparks and effectiveness. The hand crank allows for the sparks to happen.

#63

  The Layden Jar is an early device for storing electric charge that was invented in 1745 by Pieter van Musschenbroek. It was the first capacitor. It consisted of a top electrode electrically connected to metal foil coating a glass jar and a brass knob at the end. When an electrical charge is applied to the external knob, positive and negative charges accumulate from the two metal coatings respectively, but are unable to discharge because of the glass between them. The result is that the charges will hold each other in equilibrium  until a discharge path is provided.  These were first used to store electricity, but were later used as a condenser in early wireless equipment.

The Wimshurt machine is as electrostatic device for generating high voltages developed in 1880. It has two large contra-rotating discs mounted in a vertical plane. Their metal sectors rotate in the opposite direction passing the crossed metal. An imbalance in charges is induced, amplified, and collected by two pairs of metal combs. The positive feedback increases until the breakdown voltage of air is reached and a spark jumps across.

 

History of Science - Leyden Jar

The concept of the leyden jar was invented by the ancient Greeks and then expanded on by a German scientist in 1745. A typical design consists of a top electrode connected, by a chain, to a metal foil, coating part of the inner surface of a glass jar. A conducting foil is wrapped around the outside of the jar. The jar is charged by an electrostatic generator connected to the inner electrode while the outer plate is grounded. The inner and outer surfaces of the jar store equal, but opposite charges. Leyden jars are typically used to build and store electricity and is currently known as a capacitator.

? # 63

Technology was lacking in the seventeenth and eighteenth centuries compared to what is available at our fingertips today. Even so this time period had its share of science innovation. For example, in science there were ways that scientists were able to study static electricity. One of the ways they were able to do so was the Leyden jar. The Leyden jar is constructed with a glass jar that has an electrode attached to a piece of foil inside of it. Plus, there is a conducting foil is wrapped around the outside of the jar, matching the internal coated area. Finally the whole device is completed by charging it with generator. The jar works by holding the charges from the generator as they are equal but opposite.

March 4th Scribe

First we went over the test, then we found out that test corrections were due on the 5th because five week grades were due at that time as well. Then Mr. Wirth asked the question, What do you know about electricity? Their were very few responses, but the class was eager to learn the wonders of electricity. In the beginning of class we did some amber demos. then we used the rubber and glass and rubbed them against silk and fur to see the power of static electricity. This is where we found out that opposites attract and that water attracts to both rubber and glass. Then we learned about the electroscope, and how positives repel each other. Next Mr. Wirth showed us the magic water and how it attracts and repels to different materials. It is important to know that static electricity is not actually static, it is in fact moving. Also, electricity comes from matter. Another important fact to remember is that protons never leave because that would change the atomic number of the atom. Hopefully for anyone that needed a refresher or was not in class, this will be an effective tool.

03/07/08 What happened?

Some people might be asking themselves, What happened friday? I hope I can answer some of the questions regarding 5th period...the rest is up to you to remember.

The beginning of the class was revolved around checking the homework with the answers up on the overhead. Like many Fridays, it was a pretty talkative group. Conversations about physics related things of course. After about ten minutes or so of homework talk, Mr. Wirth went on to explain the mini-lab that the class was going to work on that day.

First, Mr. Wirth charges up the ruler with wool, making the ruler negative.
Next he charges the rod with the bunny skin, making the rod negative.
The reaction of two negatively charged objects to each other is <-----> repulsive.

The class broke up into groups to conduct similar experiments with the same objects to see how different charges and objects react to one another. Data was recorded in a chart and one chart was necessary per group.
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After the groups returned back to their seats, Mr. Wirth passed out graded work and showed us our weekend homework...
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Read Chapter 20 (p. 540-561)
Do problems: #1, 5, 6, 16, 18, 19, 21
DUE: Tuesday, March 11th*
*Students can either hand write or type up the homework and it will be collected and be graded.
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There is a online version of the textbook located on the physics website in the side tool bar on the homepage if you can't find your own book.
Make sure to know how to use an electroscope, if not be sure to see Mr. Wirth with questions.
That's about it. Enjoy.
-DH