# Inductance

In electromagnetism and electronics, inductance is the property of an electrical conductor by which a change in electric current through it induces an electromotive force (voltage) in the conductor. It is more accurately called self-inductance. The same property causes a current in one conductor to induce an electromotive force in nearby conductors; this is called mutual inductance.[1]

Inductance is an effect caused by the magnetic field of a current-carrying conductor acting back on the conductor. An electric current through any conductor creates a magnetic field around the conductor. A changing current creates a changing magnetic field. From Faraday's law of induction any change in magnetic flux through a circuit induces an electromotive force (voltage) across the circuit. Inductance is the ratio ${\displaystyle L}$ between this induced voltage ${\displaystyle v}$ and the rate of change of the current ${\displaystyle i(t)}$ in the circuit

${\displaystyle v=L{di(t) \over dt}}$

From Lenz's law, this induced voltage, or "back EMF", will be in a direction so as to oppose the change in current which created it. Thus inductance is a property of a conductor which opposes any change in current through the conductor. An inductor is an electrical component which adds inductance to a circuit. It typically consists of a coil or helix of wire.

The term inductance was coined by Oliver Heaviside in 1886.[2] It is customary to use the symbol ${\displaystyle L}$ for inductance, in honour of the physicist Heinrich Lenz.[3][4]In the SI system, the unit of inductance is the henry (H), which is the amount of inductance which causes a voltage of 1 volt when the current is changing at a rate of one ampere per second. It is named for Joseph Henry, who discovered inductance independently of Faraday.[5]

Electric circuits which are located close together, so the magnetic field created by the current in one passes through the other, are said to be inductively coupled. So a change in current in one circuit will cause the magnetic flux through the other circuit to vary, which will induce a voltage in the other circuit, by Faraday's law. The ratio of the voltage induced in the second circuit to the rate of change of current in the first circuit is called the mutual inductance ${\displaystyle M}$ between the circuits. It is also measured in henries.

## History

The history of electromagnetic induction, a facet of electromagnetism, began with observations of the ancients: electric charge or static electricity (rubbing silk on amber), electric current (lightning), and magnetic attraction (lodestone). Understanding the unity of these forces of nature, and the scientific theory of electromagnetism began in the late 18th century.

Electromagnetic induction was first described by Michael Faraday in 1831.[6][7] In Faraday's experiment, he wrapped two wires around opposite sides of an iron ring. He expected that, when current started to flow in one wire, a sort of wave would travel through the ring and cause some electrical effect on the opposite side. Using a galvanometer, he observed a transient current flow in the second coil of wire each time that a battery was connected or disconnected from the first coil.[8] This current was induced by the change in magnetic flux that occurred when the battery was connected and disconnected.[9] Faraday found several other manifestations of electromagnetic induction. For example, he saw transient currents when he quickly slid a bar magnet in and out of a coil of wires, and he generated a steady (DC) current by rotating a copper disk near the bar magnet with a sliding electrical lead ("Faraday's disk").[10]

It is customary to use the symbol L for inductance, in honour of the physicist Heinrich Lenz.[11][12] In the SI system, the measurement unit for inductance is the henry, with the unit symbol H, named in honor of Joseph Henry, who discovered inductance independently of, but not before, Faraday.[13]

Other Languages
Afrikaans: Induktansie
አማርኛ: እልከኝነት
asturianu: Inductancia
azərbaycanca: İnduktivlik
Bân-lâm-gú: Tiān-kám
беларуская: Індуктыўнасць
беларуская (тарашкевіца)‎: Індуктыўнасьць
български: Индуктивност
Boarisch: Induktivität
català: Inductància
čeština: Indukčnost
dansk: Induktans
Deutsch: Induktivität
Ελληνικά: Αυτεπαγωγή
español: Inductancia
Esperanto: Induktanco
euskara: Induktantzia
français: Inductance
Gaeilge: Ionduchtas
galego: Indutancia
한국어: 유도계수
हिन्दी: प्रेरकत्व
Bahasa Indonesia: Induktansi
íslenska: Span
italiano: Induttanza
עברית: השראות
latviešu: Induktivitāte
lietuvių: Induktyvumas
македонски: Индуктивност
Bahasa Melayu: Induktans
Nederlands: Zelfinductie
नेपाल भाषा: इन्डक्ट्यान्स
norsk: Induktans
norsk nynorsk: Induktans
oʻzbekcha/ўзбекча: Induktivlik
português: Indutância
română: Inductanță
Scots: Inductance
slovenčina: Indukčnosť
slovenščina: Induktivnost
српски / srpski: Самоиндукција
srpskohrvatski / српскохрватски: Samoindukcija
svenska: Induktans
தமிழ்: தூண்டம்
татарча/tatarça: Индуктивлык
Türkçe: İndüktans
Türkmençe: Induktiwlik
українська: Індуктивність
Wolof: Xiirtalu