Nuclear

Part 2 - Electricity

Otto von Guericke built a friction machine, that would continuously convert mechanical work into static electricity, in 1663. However, it was 1729 before Stephen Gray identified electrical conductors and non conductors (insulators) and 1733 before C. F. du Fay showed the difference between positive and negative electricity.

Ewald Georg von Kleist and Pieter van Musschenbroek invented the Leyden Jar (capacitor) about 1746 as a way to temporarily store a high-voltage electric charge. In 1791, Michael Faraday discovered the principles of electromagnetic induction, diamagnetism and electrolysis. In 1821, he discovered that a wire, carrying an electric current, rotated around a fixed magnet and also demonstrated a that a magnet, rotating around a conducting wire circuit, produced a current in the circuit. In 1831, he built the first electric motor, the first electrical generator and the first electrical transformer.

Alessandro Volta discovered he could create a source of electricity by immersing two dissimilar metals in a liquid solution and, in 1800, he developed the voltaic pile by stacking of alternate plates of copper and zinc separated by flannel soaked in brine or a weak solution of sulphuric acid in water. This made the zinc rod the negative electrode and the copper rod the positive electrode. When the two terminals were connected, an electric current flowed.

Volta also studied electrical capacitance, developing separate means to study both electrical potential (V) and charge (Q).  He understood that voltage (electrical potential) was the driving force causing the current to flow. The electrical unit of potential is named Volt in his honour.

Humphrey Davy used Volta's idea to devise electrolysis as a way to separate a wide range of elements from oxides and other compounds. This included not only splitting water into oxygen and hydrogen but also extracting pure metals like potassium, sodium, barium, strontium and magnesium. 

In 1802 Davy also produced a brilliant light from a continuous spark (arc) between two carbon rods, the first arc lamp. In Denmark, in 1820, Hans Christian Ørsted realized that a wire carrying an electric current was surrounded by a magnetic field. 

In 1819, Napoleon was finally defeated at the battle of Waterloo.

André-Marie Ampère, in Paris, founded the science of electrodynamics, after 1820, when  Ørsted showed that a magnetic needle was deflected by an adjacent electric current. Ampère also demonstrated the connection between his discoveries and Charles Augustin de Coulomb's law of magnetic action. Georg Simon Ohm discovered the direct relationship between current (Amperage) and electrical potential (Voltage) and also the resistance of various metals to conduct electricity (measured in Ohms). (The conductors with lowest resistance (best conductivity) are silver, copper, gold and aluminum, but, because of the cost, the most commonly used are copper and aluminum. Aluminum being used almost exclusively for high voltage transmission lines where it is supported by a steel wire cable).In 1827, the British botanist Robert Brown observed through his microscope that pollen grains floating in water constantly jiggled about for no apparent reason. This Brownian Motion, explained by Albert Einstein in 1905, was caused by the water molecules continuously knocking the grains about with random collisions.

Between 1838 and 1851, Richard Laming (1798–1879) published a series of papers speculating about the electrical properties of atoms. He was one of the first to suggest the existence of a sub-atomic particle with a unit electric charge. He imagined that the atom consisted of a core of material surrounded by concentric shells of these electrical 'atoms', or particles. He also believed that these particles could be added to, or subtracted from, an atom thereby altering its charge.

Around 1844, he suggested that an atom surrounded by "perfect external spherical strata" of electrical particles would not conduct electricity, it would be an insulator. He also supposed that chemical reactions could occur when two atoms shared an electrical charge. However, although he was presciently correct, his ideas received little interest, probably because he provided no experimental support for his theories.

In 1874, Irish physicist George Johnstone Stoney estimate the value of this elementary charge using Faraday's laws of electrolysis and, in 1881, coined the term electron.

In 1859, German physicist Julius Plücker, was studying electrical conductivity in rarefied gases. He built a sealed glass tube containing two metal plates (anode and cathode) connected across an electrical supply and pumped out the air before replacing it with the gas. He was intrigue by a phosphorescent light, on the wall of his glass tube near the cathode, that could be moved by a magnetic field. His student, Johann Wilhelm Hittorf, deduced that the phosphorescence was caused by rays emitted from the cathode that were striking the tube walls. In 1876, another German physicist, Eugen Goldstein, coined the term cathode rays.