How a changing magnetic field generates the electricity powering our world

Science · Published 22 October 2026 Swipe more like this →

In short: In 1831, Michael Faraday discovered that electricity could be harvested from motion. By simply moving a magnet near a wire, he proved that magnetism could induce a current. This fundamental principle of electromagnetic induction remains the bedrock of modern power generation and electrical engineering.

The phenomenon of electromagnetic induction occurs when a magnetic field undergoes change. Michael Faraday, an English scientist, first observed this through experimental work in 1831. He observed that opening or closing a circuit to fluctuate an electromagnet's magnetic field allowed for current detection in an adjacent conductor. Furthermore, he realised that continuous movement of a wire near a fixed magnet, or sliding a permanent magnet through a coil, generates an induced current. He specifically noted that a current could be detected in a separate, nearby conductor whenever the magnetic field around an electromagnet was made to grow or collapse.

To understand this, Faraday visualized the magnetic field as a collection of induction lines. The total number of these lines passing through a specific area is known as magnetic flux. Faraday attributed electrical effects to the changing of this flux. Later, the Scottish physicist James Clerk Maxwell expanded on this, proposing that a changing magnetic flux produces an electric field even in empty space, away from any conductors. This insight allowed Maxwell to create the mathematical expression for the induced electromotive force (emf). This fundamental concept is also known as Faraday's law of magnetic induction. This theoretical framework serves as a cornerstone for understanding how transformers and generators function in modern technology.

The law states that the magnitude of the induced emf is proportional to the rate at which the magnetic flux changes over time. Mathematically, this is expressed as emf = −dΦ/dt. If the change in flux is measured in webers per second, the resulting induced emf is measured in volts. Today, Faraday’s law is recognized as one of the four Maxwell equations that define the entirety of electromagnetic theory. This relationship is a vital component of the four Maxwell equations that constitute the foundation of electromagnetic theory.

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