Classical electromagnetism
Theory · 1820s to 1870s, Britain and continental Europe · Physics, stage 2: Map the theories
Classical electromagnetism unified electricity, magnetism, and light into one account. Faraday, working experimentally and with almost no mathematics, showed that a changing magnetic field produces an electric current and proposed that space around a magnet is filled with lines of force. Maxwell put Faraday's picture into equations in the 1860s and found that they predicted waves travelling at a speed matching the measured speed of light, which established that light is an electromagnetic wave. The theory is complete and accurate for everything above atomic scale, but its equations do not transform correctly under the old rules for changing between moving frames, and resolving that mismatch produced special relativity.
What it claims
- Electric and magnetic effects are two aspects of a single field.
- A changing magnetic field creates an electric field, and a changing electric field creates a magnetic field.
- The combination propagates as a wave through empty space at a fixed speed.
- Light is such a wave, so optics is a branch of electromagnetism.
Key ideas
People
Sources
- Classical electromagnetism English Wikipedia
- Maxwell's equations English Wikipedia
- Electromagnetism Britannica
