Ørsted's effect: electric current deflects a compass

What was discovered

During a lecture Ørsted observes that a current-carrying wire deflects a magnetised needle: electricity produces magnetism. It is the birth of electromagnetism and the first connection between two forces considered independent.

Announced in Latin in July 1820; within weeks Ampère and Arago reproduced and extended the result in Paris.

What it led to

• Ampère's law and the Biot-Savart law
• Electromagnet (Sturgeon, 1825) and the galvanometer
• Faraday's induction
• Maxwell's equations

Built on

• Voltaic pile
• Naturphilosophie (unity of forces)

Made possible

• Multiplier galvanometer (Schweigger)1820
• Ampère's law and electrodynamics1820-1827
• Biot–Savart law1820
• Electric motor1821-1834
• Thermoelectricity (Seebeck and Peltier effects)1821
• Arago's disc (rotational magnetism)1824
• Electromagnet1824-1825
• Electromagnetic induction1831
• Electromagnetic telegraph

Links