For an explanation, see the main splats page
SPLATS about electrostatics
The principles of electrostatics
- Static electricity shows attraction and repulsion: the forces obey the inverse square law, the force being inversely proportional to the square of the distance.
- Electrostatic charges can accumulate on the outside of insulators, but the charges cannot move freely over the surface, or through the insulators.
- A charge which exists on an object is called a static charge because it does not move, but it is still capable of moving if a path is available.
- Static electricity is most easily generated by friction, but it may also be generated by induction with an electrophorus which has been charged by friction.
- An electrostatic charge may be induced in conducting material: this is the basis of the operation of the electrophorus, an early electrostatic device.
- Objects like a balloon, comb, and other common objects made from insulating materials can be charged, simply by rubbing them against another insulator.
- A Leyden jar was an early form of capacitor, a device for holding static charge and allowing crude experiments on the flow of brief currents.
- A capacitor can be used to store a static charge and the capacitance of a capacitor depends on the dielectric of the medium separating the two charges.
- Lightning is caused by the build-up of static charge, it carries a great deal of energy, and it has good and bad effects, fixing nitrogen and starting fires
- Lightning is a form of static electricity, and thunder is caused by air being heated and expanding suddenly along the flash when the charge breaks down.
- A Faraday cage is a metal screen that can protect somebody from lightning because it isolates them from charge on the outside. The cages also block radio waves.
- In 1660 Otto von Guericke developed an electrostatic machine to generate charge. It was made by charging a ball of sulfur with static electricity.
- In 1675, Jean Picard was carrying a barometer through the darkened streets of Paris, when he noticed a faint glow in the empty space above the mercury.
- In 1702 Francis Hauksbee noticed rarefied air glows during an electrical discharge through a vacuum, and showed this to the Royal Society the following year.
- In 1729, Stephen Gray used string to send an electrostatic signal in a barn, over a distance of 293 feet along a fine thread, the first telegraph.
- In 1746 Abbé Nollet showed that electricity travels at an apparently instantaneous speed around a mile-circumference circle of monks, linked to a Leyden jar.
- In 1775, a Royal Navy gunpowder magazine suffered a lightning strike at Purfleet in England, in spite of the fact that it was fitted with lightning rods.
- We know now that static charge accumulates better at the point of a lightning rod, but the Purfleet strike was used to claim that knobby ends were better.
- In 1785, Charles Coulomb showed that electrostatic repulsion and attraction are related to the product of the charges and the inverse square of the distance.
- If Benjamin Franklin ever flew a kite in a thunderstorm to attract lightning, he did so in 1749: he certainly wrote about doing so in that year, and in 1752.
- The next person to fly a kite in a thunderstorm after Franklin published his account was killed. Sometimes, a thought experiment or a better design is needed.
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