Electricity
In 2750 BCE, ancient Egyptian texts described electric fish as the protectors of all other fish. These early records show that people knew about shocks from living creatures long before they understood electricity itself. Ancient Greek and Roman naturalists reported these same phenomena millennia later. Pliny the Elder and Scribonius Largus wrote about the numbing effect of electric catfish and electric rays. They observed that such shocks could travel along conducting objects. Patients suffering from gout or headaches were sometimes directed to touch these fish hoping the powerful jolt would cure them.
Around 600 BCE, Thales of Miletus made a series of observations on static electricity. He believed that rubbing amber with fur rendered it magnetic. This was incorrect because magnetite needed no rubbing to attract objects. Later science proved a link between magnetism and electricity anyway. The Parthians may have had knowledge of electroplating based on the Baghdad Battery discovered in 1936. This artifact resembles a galvanic cell though its electrical nature remains uncertain.
William Gilbert wrote De Magnete in 1600 making a careful study of electricity and magnetism. He distinguished the lodestone effect from static electricity produced by rubbing amber. Gilbert coined the Neo-Latin word electricus meaning of amber or like amber. This association gave rise to the English words electric and electricity which first appeared in print in Thomas Browne's Pseudodoxia Epidemica of 1646.
Benjamin Franklin conducted extensive research in electricity during the 18th century selling his possessions to fund his work. In June 1752 he is reputed to have attached a metal key to the bottom of a dampened kite string. He flew the kite in a storm-threatened sky showing sparks jumping from the key to his hand. Lightning was indeed electrical in nature according to this experiment though it is uncertain if Franklin personally carried it out. He explained the paradoxical behavior of the Leyden jar as a device for storing large amounts of electrical charge.
Hugh Williamson reported experiments to the Royal Society in 1775 on shocks delivered by the electric eel. That same year John Hunter described the structure of the fish's electric organs. Luigi Galvani published his discovery of bioelectromagnetics in 1791 demonstrating that electricity passed signals to muscles. Alessandro Volta created a battery called the voltaic pile in 1800 using alternating layers of zinc and copper.
Hans Christian Ørsted and André-Marie Ampère recognized electromagnetism in 1819, 1820. Michael Faraday invented the electric motor in 1821 while Georg Ohm mathematically analyzed the electrical circuit in 1827. James Clerk Maxwell definitively linked electricity and magnetism through On Physical Lines of Force in 1861 and 1862. Albert Einstein published a paper explaining experimental data from the photoelectric effect in 1905 earning him the Nobel Prize in Physics in 1921.
The late 19th century saw the greatest progress in electrical engineering through figures like Thomas Edison and Nikola Tesla. Alexander Graham Bell, Ottó Bláthy, Galileo Ferraris, Oliver Heaviside, Ányos Jedlik, William Thomson, Charles Algernon Parsons, Werner von Siemens, Joseph Swan, Reginald Fessenden, and George Westinghouse turned electricity into an essential tool for modern life. Heinrich Hertz discovered that electrodes illuminated with ultraviolet light create electric sparks more easily in 1887.
Sir Charles Parsons invented the steam turbine in 1884 to convert thermal energy of steam into rotary motion. This device is still used today by electro-mechanical generators. The invention of the transformer in the late nineteenth century meant power could be transmitted efficiently at higher voltage but lower current. Efficient transmission allowed electricity to be generated at centralized power stations where it benefited from economies of scale.
Demand for electricity grew rapidly as nations modernized. The United States showed a 12% increase in demand during each year of the first three decades of the twentieth century. Public utilities were set up in many cities targeting the burgeoning market for electrical lighting. The incandescent light bulb invented in the 1870s became one of the first publicly available applications of electrical power.
By modern convention the charge carried by electrons is defined as negative while protons carry positive charge. Benjamin Franklin had defined positive charge as being acquired by a glass rod rubbed with silk cloth before these particles were discovered. A proton carries a charge of exactly 1.602 x 10^-19 coulombs known as the elementary charge. No object can have a charge smaller than this value and any amount of charge is a multiple of it.
Charles-Augustin de Coulomb investigated phenomena in the late eighteenth century deducing that like-charged objects repel and opposite-charged objects attract. The force acts on charged particles themselves hence charge tends to spread evenly over conducting surfaces. Coulomb's law relates the electromagnetic force to the product of charges having an inverse-square relation to distance between them. The electromagnetic force pushing two electrons apart is 10^42 times stronger than gravitational attraction pulling them together.
Michael Faraday introduced the concept of the electric field created by a charged body in surrounding space. An electric field results in a force exerted on any other charges placed within it. Field lines originate at positive charges and terminate at negative charges entering good conductors at right angles. Air tends to arc across small gaps at electric field strengths exceeding 30 kV per centimeter causing lightning when clouds separate charge.
Electrical power is usually generated by electro-mechanical generators driven by steam from fossil fuel combustion or nuclear reactions. Steam turbines convert thermal energy into rotary motion used by these generators. Electricity generated by solar panels relies on converting solar radiation directly into electricity using the photovoltaic effect. Wind farms use kinetic energy of wind to drive generators increasingly important in many countries today.
The transformer invention allowed electrical power to be transmitted more efficiently at higher voltage but lower current. Efficient transmission meant electricity could be despatched relatively long distances from centralized stations where needed. Normally demand for electricity must match supply as storage remains difficult. A certain amount of generation must always be held in reserve to cushion an electrical grid against disturbances.
Storage plays an increasing role bridging gaps between variable renewable energy sources like wind and solar. Four types of energy storage technologies exist including batteries chemical storage such as hydrogen thermal or mechanical pumped hydropower. The United States showed a 12% increase in demand during each year of the first three decades of the twentieth century. Emerging economies such as India or China now experience similar rates of growth.
The first solid-state device was the cat's-whisker detector first used in the 1900s in radio receivers. A whisker-like wire is placed lightly in contact with a solid crystal such as germanium to detect radio signals. Current flow can be understood as negatively charged electrons and positively charged electron deficiencies called holes. These charges are understood in terms of quantum physics using crystalline semiconductors as building materials.
Solid-state electronics came into its own with transistor technology emerging at Bell Labs in 1947. John Bardeen and Walter Houser Brattain invented the first working germanium-based point-contact transistor followed by the bipolar junction transistor in 1948. A modern integrated circuit may contain many billions of miniaturized transistors in a region only a few centimeters square.
Electronic devices make use of vacuum tubes transistors diodes sensors and integrated circuits performing electron control. Nonlinear behavior of active components makes digital switching possible widely used in information processing telecommunications and signal processing. Interconnection technologies like circuit boards transform mixed components into regular working systems enabling complex functionality across global networks.
A voltage applied to a human body causes an electric current through tissues though the relationship is non-linear. The threshold for perception varies with supply frequency and path of current being about 0.1 mA to 1 mA for mains-frequency electricity. If current is sufficiently high it will cause muscle contraction fibrillation of heart and tissue burns. Death caused by electric shock remains used for judicial execution in some US states though very rare by end of 20th century.
Electricity occurs naturally as lightning observed in several forms in nature. Many interactions familiar at macroscopic level such as touch friction or chemical bonding are due to atomic-scale electric field interactions. Earth's magnetic field results from natural dynamo of circulating currents in planet core. Certain crystals like quartz generate potential difference across faces when pressed known as piezoelectricity discovered in 1880 by Pierre and Jacques Curie.
Some organisms detect changes in electric fields known as electroreception while others termed electrogenic generate voltages themselves serving as predatory weapons. Electric eels detect or stun prey via high voltages generated from modified muscle cells called electrocytes. All animals transmit information along cell membranes with voltage pulses called action potentials coordinating activities between neurons and muscles.
Common questions
When did ancient Egyptian texts first describe electric fish?
Ancient Egyptian texts described electric fish as protectors of all other fish in 2750 BCE. These early records show that people knew about shocks from living creatures long before they understood electricity itself.
Who coined the word electricity and when did it appear in print?
William Gilbert coined the Neo-Latin word electricus meaning of amber or like amber in his book De Magnete published in 1600. The English words electric and electricity first appeared in print in Thomas Browne's Pseudodoxia Epidemica of 1646.
What experiment did Benjamin Franklin conduct to prove lightning is electrical?
In June 1752 Benjamin Franklin attached a metal key to the bottom of a dampened kite string and flew it in a storm-threatened sky. He showed sparks jumping from the key to his hand proving that lightning was indeed electrical in nature according to this experiment.
Which scientists discovered electromagnetism and when did they make their findings public?
Hans Christian Ørsted and André-Marie Ampère recognized electromagnetism in 1819 and 1820 respectively. Michael Faraday invented the electric motor in 1821 while Georg Ohm mathematically analyzed the electrical circuit in 1827.
How much charge does a single proton carry and what is this value called?
A proton carries a charge of exactly 1.602 x 10^-19 coulombs known as the elementary charge. No object can have a charge smaller than this value and any amount of charge is a multiple of it.