Ampère's law and electrodynamics

What was discovered

Two parallel currents attract or repel each other depending on their direction, with a force that Ampère formulates mathematically; magnetism is reduced to electric currents (even that of magnets, through molecular currents). It founds electrodynamics.

Biot and Savart formulated the law for the field of a wire in 1820; Ampère published the synthesis in 1827.

What it led to

• Maxwell's equations (Ampère-Maxwell law)
• Electron theory of magnetism
• Unit of current (ampere)
• Design of electromagnets and motors

Built on

• Coulomb's law1785
• Ørsted's effect: electric current deflects a compass1820
• Laplace's mathematical analysis

Made possible

• Electric motor1821-1834
• Electromagnet1824-1825
• Electromagnetic induction1831
• Maxwell's equations1861-1865
• Solenoid

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