Electricity is a broad term encompassing the family of phenomenon arising from interaction between charged particles. Of the four fundamental forces of nature, the electromagnetic force is the most influential in our everyday lives. It is responsible for holding materials together, interaction between objects, and even light. Although the existence of electrical phenomenon have been known since ancient times, the properties of electricity have been known to science for less than three hundred years. Even so, almost all modern inventions utilize electricity in some way.
Electrically-charged particles fall under two categories, positive and negative. All positively-charged particles repel all other positively-charged particles, yet attract negatively-charged particles. Likewise, all negatively-charged particles repel each other while attracting positively-charged particles. Thus, no three electrically-charged particles can simultaneously attract one another. The strength of attraction (or repulsion) is inversely proportional the the square of the distance between the particles. Therefore, objects that consist of an equal amount of positively- and negatively-charged particles display an overall net electric charge of zero at distances much greater than the distance between the charged particles themselves. In everyday life, the positively charged particles that we encounter are the protons in the nucleus of the atom, and the negatively charged particles that we encounter are the electrons surrounding the nucleus. As even the smallest distances that humans can perceive are orders of magnitude above the atomic radius, we do not usually perceive electrical interactions directly. However, the movement of electrons as electric current is very influential in modern life, and is very apparent to unaided observation. Similarly, magnetic and chemical interactions are easily observed, and both of these phenomenon are based upon the interaction between electrically-charged atomic particles.
The first suspected human application of electricity is the ancient Egyptian Dendera Light, dating to about 300 BC. The Baghdad Battery, dating between 250 BC and 640 AD, may be another ancient electrical device. The ancient Greeks were the first to record knowledge of electrical phenomenon in their writings. They observed both lightning and static electricity, however they did not make any logical connections between the two. Chinese scientists wrote about the use of magnetite as an alternative to celestial navigation. However, it was not until the 17th century that scientists began actively investigating electricity. Otto von Guericke developed the first electrostatic generator in 1660, and Pieter van Musschenbroek invented the electrical capacitor in 1745. These two inventions provided scientists with on-demand electrical current, thus facilitating controlled experimentation. The work of Nikola Tesla and Thomas Edison brought electrical devices to everyday use.
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