André-Marie Ampère (20 January 1775 – 10 June 1836) was a French physicist andmathematician who is generally regarded as one of the main founders of the science ofclassical electromagnetism, which he referred to as "electrodynamics". The SI unit of measurement of electric current, the ampere, is named after him.
Biography
Ampère was born on 20 January 1775 to Jean-Jacques Ampère, a
prosperous businessman, and Jeanne Antoinette Desutières-Sarcey Ampère during
the height of theFrench Enlightenment. He spent his childhood and adolescence
at the family property atPoleymieux-au-Mont-d'Or near
Lyon. Jean-Jacques Ampère, a successful merchant, was an admirer of the
philosophy of Jean-Jacques Rousseau, whose theories of education (as
outlined in his treatise Émile) were the basis of Ampère’s education.
Rousseau believed that young boys should avoid formal schooling and pursue
instead an “education direct from nature.” Ampère’s father actualized this
ideal by allowing his son to educate himself within the walls of his
well-stocked library. French Enlightenment masterpieces such asGeorges-Louis
Leclerc, comte de Buffon’s Histoire naturelle, générale et
particulière (begun in 1749) and Denis Diderot and Jean le
Rond d'Alembert’s Encyclopédie (volumes added between 1751 and 1772)
thus became Ampère’s schoolmasters. The young Ampère, however, soon resumed
his Latin lessons, which enable him to master the works ofLeonhard
Euler and Daniel Bernoulli.
Work in electromagnetism
In September of 1820, Ampère’s friend and eventual
eulogist François Arago showed the members of the French Academy of
Sciences the surprising discovery of Danish physicist Hans
Christian Ørsted that a magnetic needle is deflected by an
adjacent electric current. Ampère begun developing a mathematical and
physical theory to understand the relationship
between electricity and magnetism. Furthering Ørsted’s
experimental work, Ampère showed that two parallel wires carrying electric
currents attract or repel each other, depending on whether the currents flow in
the same or opposite directions, respectively - this laid the foundation of
electrodynamics. He also applied mathematics in generalizing physical laws from
these experimental results. The most important of these was the principle that
came to be called Ampère’s law, which states that the mutual action of two
lengths of current-carrying wire is proportional to their lengths and to the
intensities of their currents. Ampère also applied this same principle to
magnetism, showing the harmony between his law and French
physicist Charles Augustin de Coulomb’s law of magnetic action. Ampère’s
devotion to, and skill with, experimental techniques anchored his science
within the emerging fields of experimental physics.
Ampère also provided a physical understanding of the
electromagnetic relationship, theorizing the existence of an “electrodynamic
molecule” (the forerunner of the idea of the electron) that served as the
component element of both electricity and magnetism. Using this physical
explanation of electromagnetic motion, Ampère developed a physical account of
electromagnetic phenomena that was both empirically demonstrable and
mathematically predictive. In 1827 Ampère published his magnum
opus, Mémoire sur la théorie mathématique des phénomènes électrodynamiques
uniquement déduite de l’experience (Memoir on the Mathematical Theory of
Electrodynamic Phenomena, Uniquely Deduced from Experience), the work that
coined the name of his new science, electrodynamics, and became known ever
after as its founding treatise. In 1827 he was elected a Foreign Member of
the Royal Society and in 1828, a foreign member of the Royal Swedish
Academy of Science. In recognition of his contribution to the creation of
modern electrical science, an international convention signed in 1881
established the ampere as a standard unit of electrical measurement,
along with the coulomb, volt, ohm, and watt, which are named,
respectively, after Ampère’s contemporaries Charles-Augustin de
Coulomb of France,Alessandro Volta of Italy, Georg
Ohm of Germany, and James Watt of Scotland.
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