Oersted's 1820 experiment showed that a current-carrying wire produces a noticeable effect on a nearby

1. NCERT §4.1 (Introduction): Hans Christian Oersted, in summer 1820, noticed that a current in a straight wire deflected a nearby magnetic compass needle. 2. This was the first direct demonstration that ELECTRICITY produces a MAGNETIC field — until then the two were thought to be distinct phenomena. 3. Oersted's experiment launched the field of ELECTROMAGNETISM and led to the work of Ampere, Faraday, and ultimately Maxwell's unification of electricity and magnetism. 4. Other options describe different physical effects unrelated to Oersted's observation. _Source: NCERT Class 12 Physics Part 1, Ch 4 "Moving Charges and Magnetism", §4.1 (Introduction), p. 1._