Introduction

The Historical Context: From Separate to Unified

For a long time, electricity and magnetism were treated as two completely separate phenomena. This changed in the early 1800s, when Oersted, Ampere, and others showed through experiments on electric current that the two are related: moving electric charges produce magnetic fields. A simple example is a current-carrying wire deflecting a nearby compass needle.

This naturally raised the reverse question: can a moving magnet (a changing magnetic field) produce an electric current?

The Discovery of Electromagnetic Induction

Around 1830, Michael Faraday in England and Joseph Henry in the USA — working independently — answered this with a resounding yes. Their experiments conclusively demonstrated that electric currents are induced in closed coils whenever they are subjected to changing magnetic fields. This is the phenomenon this chapter studies, and it is called electromagnetic induction.

Faraday's "Newborn Baby" Reply

When Faraday first showed that relative motion between a bar magnet and a wire loop produced a small current in the loop, he was famously asked, "What is the use of it?" His reply: "What is the use of a new born baby?" — meaning a discovery's value isn't always obvious at first, but can grow into something transformative.

Why It Matters

Electromagnetic induction is not just a theoretical curiosity — it underpins practical technology everywhere. Picture a world with no electric lights, no trains, no telephones, and no computers: that is roughly what a world without this discovery would look like. The pioneering work of Faraday and Henry led directly to today's generators and transformers, and much of modern civilisation's progress traces back to the discovery of electromagnetic induction.