Physicist — Heinrich Friedrich Emil Lenz (1804–1865) was a Russian physicist of German origin, born in Dorpat (now Tartu, Estonia), then part of the Russian Empire. After studying in Dorpat he took part as a young man in a round-the-world expedition, during which he carried out geophysical and oceanographic measurements. He became professor at the University of St Petersburg, where he devoted himself to electromagnetism and thermal phenomena. His most famous contribution is the 1834 law on the direction of induced currents, which completes Faraday’s law of induction by supplying the minus sign and translating the principle of conservation of energy into electromagnetism. He also studied the dependence of electrical resistance on temperature and, with Joule, the heat produced by currents.
Trivia
As a young scientific officer he took part in Captain Otto von Kotzebue’s round-the-world expedition (1823–1826), carrying out the first systematic measurements of ocean salinity and temperature at depth.
Theories and contributions
- Lenz’s law — The induced current flows in the direction that opposes the change in flux that produces it; it supplies the sign in the Faraday-Neumann-Lenz law .
- Joule-Lenz effect — The heat dissipated by a current-carrying conductor is proportional to the square of the current: .
Present in chapters
Linked atoms
19 linked atoms.
17 Il campo magnetico
18 Induzione elettromagnetica
- Faraday’s resolution
- Circulation of E and the Faraday-Neumann-Lenz law
- The fictitious generator
- Outline for solving an induction problem
- Lenz’s law as an autonomous principle
- Lenz as magnetic inertia
- Three experiments showing Lenz’s law at work
- Direction of the current: two quick cases
- Eddy currents
- Lenz’s minus sign
- The alternator and sinusoidal EMF
- When the electric field stops being conservative
19 Le equazioni di Maxwell e le onde elettromagnetiche
- The four equations (first, incomplete version)
- The displacement current
- Maxwell’s four equations
- The transformer