A correlation is a single numerical value that is used to describe the relationship between two variables. All correlations have strength and direction. When two variables have a positive correlation, that means the two variables move in the same direction. The closer a positive correlation is to 1, the stronger it is.
William Gilbert discovered electricity, not Nikola Tesla. Nikola Tesla invented things. not discovered electricity. Again, William Gilbert discovered it and named it. He did this in the 1600s. It wasn't Nikola Tesla.
History of Electricity-Early Inventors. Otto von Guericke proved that a vacuum could exist. Creating a vacuum was essential for all kinds of further research into electronics. In 1660, Otto von Guericke invented a machine that produced static electricity, this was the first electric generator. In 1729, Stephen Gray discovered the principle of the conduction of electricity. In 1733, Charles Francois du Fay discovered that electricity comes in two forms which he called resinous (-) and vitreous (+), now called negative and positive.