Inductance

Lore & Background

The history of electromagnetic induction began with ancient observations of static electricity, lightning, and magnetic attraction. The scientific theory of electromagnetism was initiated and achieved during the 19th century. In his experiment, he wrapped two wires around opposite sides of an iron ring and observed a transient current in the second coil when a battery was connected or disconnected from the first coil. He also saw transient currents when sliding a bar magnet in and out of a coil and generated a steady DC current by rotating a copper disk near a bar magnet with a sliding electrical lead, known as Faraday's disk.

Reader's Guide

Inductance is a key concept in electromagnetism, representing the property of a conductor or circuit to oppose changes in current through it. This opposition arises from the induced voltage (back EMF) created by a changing magnetic field, as described by Faraday's law and Lenz's law. The inductance of a circuit depends on its geometry and the magnetic permeability of nearby materials; ferromagnetic materials like iron can increase inductance by thousands of times. An electronic component designed to add inductance is called an inductor, typically a coil or helix of wire. Inductance is also the basis for mutual inductance, where a change in current in one circuit induces a voltage in another, enabling devices like transformers.

Did You Know?

• The symbol L for inductance is used in honor of physicist Heinrich Lenz.
• The unit of inductance, the henry (H), is named after Joseph Henry, who discovered inductance independently of Faraday.
• A coiled wire has higher inductance than a straight wire because magnetic field lines pass through the circuit multiple times, creating multiple flux linkages.