Georg Ohm

Whose Proportion Was Called A Fancy · Physicist & Schoolmaster · 1789–1854

The Gymnasium teacher who measured what a wire does to a current, expressed it as a proportionality, and was told by the learned journals that his book was a web of naked fancies.

Who was Ohm?

Georg Simon Ohm was born at Erlangen in 1789, the son of a locksmith who had taught himself mathematics and taught it to his sons. He spent most of his working life as a schoolmaster rather than a professor, and the research he is remembered for was done in the laboratory of a Gymnasium in Cologne. Between 1825 and 1827 he measured how the current in a circuit depends on the conductor, drawing wires of the same metal to different lengths and cross-sections and using the deflection of a magnetic needle as his measure; Thomas Seebeck's newly invented thermocouple gave him a steady source where the voltaic pile had drifted maddeningly. In 1827 he published Die galvanische Kette, mathematisch bearbeitet, setting out the proportionality between the current, the driving force and the resistance of the whole circuit. The reception in Germany was hostile: reviewers dismissed the mathematical treatment as fanciful, the Prussian minister of education thought such a physicist unfit to teach, and Ohm resigned his post. Recognition came from abroad — the Royal Society awarded him the Copley Medal in 1841 and elected him a foreign member the following year — and he did not obtain a full professorship, at Munich, until 1852, two years before his death. The unit of resistance was named after him in 1881.

Major achievements

• Established the proportionality between current, driving force and resistance in a circuit
• Showed how the resistance of a conductor depends on its length and its cross-section
• Published Die galvanische Kette, mathematisch bearbeitet in 1827
• Used Seebeck's thermocouple to obtain a steady source where the voltaic pile drifted
• Awarded the Copley Medal by the Royal Society in 1841, when Germany had rejected the work

Life in brief

• 1789 — Born at Erlangen: Son of a self-taught locksmith who taught his sons mathematics.
• 1817 — Teaching at Cologne: A Gymnasium post with a laboratory attached.
• 1826 — The measurements: Wires of different lengths and thicknesses, and a thermocouple that holds steady.
• 1827 — Die galvanische Kette: The proportionality published — and savaged.
• 1828 — Resigns his post: Years without a position follow.
• 1841 — Copley Medal: London honours what Berlin dismissed.
• 1852 — Professor at Munich: A full chair at sixty-three.
• 1854 — Dies at Munich: The unit is named after him twenty-seven years later.

Explore the life of Ohm — five chapters

1. A Locksmith Who Taught Himself Mathematics — Erlangen, and an education from a father
2. A Source That Holds Steady — Why the voltaic pile made the measurement impossible
3. Length and Thickness — The relationship, 1827
4. A Web of Naked Fancies — The reception, and a resignation
5. London Honours What Berlin Dismissed — The Copley Medal, and a chair at sixty-three

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