Ohm's law

What was discovered

The current flowing through a conductor is proportional to the applied voltage and inversely proportional to its resistance. It is the basic law of electrical circuits and gives quantitative sense to 'electromotive force'.

Cavendish had found it around 1781 without publishing it; Ohm was dismissed in Germany until the Copley Medal of 1841.

What it led to

• Circuit theory (Kirchhoff's laws, 1845)
• Electrical engineering
• Long-distance telegraphy
• Electronics
• Quantitative design of telegraph lines and submarine cables
• The system of electrical units (ohm, volt, ampere, 1881)
• Electrical engineering as a discipline

Built on

• Voltaic pile1800
• Multiplier galvanometer (Schweigger)1820
• Seebeck thermocouple (stable source)
• Analogy with Fourier's heat conduction
• Seebeck thermopile
• Fourier's theory of heat

Made possible

• Wheatstone bridge1833 / 1843
• Joule's law (Joule heating)diciembre de 1840
• Kirchhoff's circuit laws1845
• Transatlantic telegraph cable1858 / 1866
• Reliable electric telegraph
• Calibrated resistors
• Electric lighting
• Transatlantic cable (Kelvin's theory)
• Electricity distribution network
• Electrical measuring instruments

📄 Original publication

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