
1570


William Gilbert (15401603) demonstrates attractive and repulsive force from rubbing many substances together (electrostatic charge); calls them "electrics," and suggests the earth itself is a magnet.

1660s

Otto von Guericke (160286) constructs first friction machine to generate static charge, using a revolving ball of sulphur.

1729

Stephen Gray (16961736) conducts experiments that show electricity moves.

1740s

Benjamin Franklin (170690) proposes the notion of positive and negative charge, conserving a balance except when a deficit is brought about by some means. His famous kite experiments, identifying lightning as a form of electrical discharge, take place in 1752.

1745

Georg von Kleist (c.170048) and Pieter van Musschenbroek (16921761) invent the Leyden jar, the first condenser (capacitor).

1759

Franz Maria Aepinus (17241802) presents the first mathematical treatment of electrical forces and constructs first condenser with parallel plates.

1770s

Henry Cavendish (17311810) anticipates later work of Coulomb and Ohm, but shuns publication. The concepts of potential difference and a zero reference point, a ground, are his.

1785

Charles Augustin de Coulomb (17361806) works out reciprocal law of electrical force (varying inversely as the square of distance between two charges).

1791

Luigi Galvani (173798) demonstrates electrical activity in living tissue, as in muscle and nerve.

1800

Alessandro Volta (17451827) invents an electric battery, the first source of DC current.

1819

Hans Christian Oersted (17771851) finds that current in a wire can deflect a nearby magnetic needle.

1820

Andre Ampere (17751836) discovers that two wires carrying currents act as magnets to attract or repel each other; he describes the relation between current direction and magnetic field orientation.

1826

Georg Simon Ohm (17891854) mathematically unites current, voltage, and resistance in the famous "law" bearing his name: V=IR.

1829

Joseph Henry (17971878) constructs an electromagnet that can lift in excess of a ton. Demonstrates a telegraph in 1831. Independently he works out principles of magnetic induction at about the same time as Faraday, but publishes slightly later.

1831

Michael Faraday (17911867) experimentally characterizes magnetic induction. The most thorough of early electrical investigators, he formulates the quantitative laws of electolysis, the principles of electric motors and transformers, investigates diamagnetic materials, and posits a physical reality for the indirectly observed magnetic and electrical lines of force.

1833

Wilhelm Weber (18041891) and Karl Friedrich Gauss (1771851) successfully operate a telegraph between two distant buildings. They devise the first system of consistent units for electrical measurement. Gauss organizes a European network of observers to record strength and direction of the geomagnetic field.

1834

Heinrich Lenz (180465) discovers, at about the same time as Henry and Faraday, that an induced current flows in a direction to oppose the change that induced itLenz's law.

1845

Gustav Robert Kirchhoff (182487) publishes "circuit rules" for calculating electrical quantities in loop and junction configurationsthe sum of all potential drops is always zero.

1851

Heinrich Ruhmkorff (180377) invents doublywound induction coil; some models produce arcs a foot or more in length. This leads to development of AC transformers.

1864

James Clerk Maxwell (183179) describes electromagnetic field in four classic equations, which allow also calculation of the speed of light. Their solution predicts waves within the field.

1869

William Crookes (18321914) and Johann Wilhelm Hittorf (18241914) independently discover "cathode rays," working with currents in glass tubes of improved vacuum quality.

1888

Heinrich Hertz (185794) discovers and measures the waves, radio waves, predicted by Faraday and Maxwell.

1888

Nikola Tesla (18671943) invents the first practicable AC motor and polyphase power transmission system, which revolutionizes industry and commerce.

1900s

Charles Proteus Steinmetz (18651923) contributes mathematical analysis of more complex nature of AC circuits.
