1.1 Background Research
Our research into storing static electricity is drawn from attempts to store lightning, such as the famous experiment by Benjamin Franklin to run lightning along a wire. Our research is a high-tech variant of that in which we use a Van de Graaff generator to generate lightning and run that electricity from a wire into a leyden jar, a cheaper alternative to buying an actual capacitor.
The idea of a Leyden Jar was thought of by two parties, Ewald Georg von Kleist, Musschenbroek and Cunaeus independently of each other at around the same time. They thought of electricity as a fluid and tried to store it in a jar like water. In 1744, von Kleist built a Leyden Jar and tested it. He was shocked when he touched the Leyden Jar and was convinced that it could hold a substantial amount of charge. Musschenbroek and Cunaeus discovered the Leyden Jar around the same time as well. (Dhogal, 1986) Musschenbroek named it the Leyden jar, after the University of Leiden where Musschenbroek worked. (Houston, 1905) He also wrote, "I would not take a second shock for the kingdom of France. (Williams, 1999)
[Fig 1.1.1] A cross-section of a leyden jar [Fig 1.1.2] A modern depiction of the cross-section of a Leyden Jar
A Leyden Jar is the original form of the capacitor, made to store static electricity. A normal design usually is made of a glass jar with conducting metal foil or salt water on the inside(Inner conductor) and foil outside of the jar(Outer conductor). A rod electrode protrudes out of the jar and is connected to the inner conductors as to allow the Leyden Jar to be charged. (Wikipedia)
To charge a Leyden Jar, a static electricity generator such as an Wimshurst or Van de Graaff machine has to be connected to the metal rod(electrode) on the top. This allows the metal foil on the inside of the Leyden Jar to be charged. The outer foil should be grounded, so that it gains an opposite charge. (Wikipedia)
The amount of electricity that can be stored in a Leyden Jar depends on the capacitance of the Leyden Jar. The area of the foil, the type of material between the two foils and the thickness of the foil all affect the capacitance of the jar.
The modern capacitor, which is used in almost all modern electrical appliances, was actually based on a very old invention, the leyden jar. Although the leyden jar is actually very old, it is still made by hobbyists today as it’s construction is very cheap and it has many uses. A leyden jar stores static electricity between 2 poles, namely, the outer and inner conductor.. When the two electrodes are connected by a wire or conducting material, an electrical spark is released. This spark contains high voltage but low current. Therefore, a leyden jar can potentially be fatal when touched. One must be careful when handling the jar so as not to injure oneself.
1.2 Research Question
Measure a value: Experimental research (I)
Investigation on the factors that affect the storage capacity of Leyden Jars.
Due to the broader range of our setup, we have decided to do more than one hypothesis.
The greater the concentration of salt, the greater the amount of short circuit voltage storable by the Leyden Jar.
The larger the surface area covered by the outer foil, the more amount of electricity the jar can store.
1.3.1 Independent variable(s)
For hypothesis 1 the independent variable we have chosen is :
The concentration of salt in the water in the jar.
For Hypothesis 2 the independent variable we have chosen is:
The surface area of the jar covered by foil.
1.3.2 Dependent variable
The dependent variables we have chosen for Hypotheses 1 & 2 are:
Amount of short-circuit voltage stored by Leyden Jars (V)
The following are the variables we will be keeping constant
Type of jar
Daiso plain glass jar, no stickers.
Time used to charge jars
Material of jars
Brand of aluminium foil
Diamond Aluminium Foil
Type of van de graaff generator
socket used to charge generator
Standard 3-pin electrical socket
Amount of salt used(Salt water leyden jar)
Volume of water used(Salt water leyden jar)
Length of electrode used
Material of electrode
Temperature of room
19 Degrees Celcius
Length of crocodile wires used.
Thickness of electrode wire(no insulation)
Thickness of insulation
Glass Jar measurements
Glass Jar cap measurements