Editing Inductor (section)

====Toroidal-core inductor====
{{main|Toroidal inductors and transformers}}
[[File:3Com OfficeConnect ADSL Wireless 11g Firewall Router 2012-10-28-0869.jpg|thumb|Toroidal inductor in the power supply of a wireless router]]

In an inductor wound on a straight rod-shaped core, the [[magnetic field lines]] emerging from one end of the core must pass through the air to re-enter the core at the other end. This reduces the field, because much of the magnetic field path is in air rather than the higher permeability core material and is a source of [[electromagnetic interference]]. A higher magnetic field and inductance can be achieved by forming the core in a closed [[magnetic circuit]]. The magnetic field lines form closed loops within the core without leaving the core material. The shape often used is a [[toroid]]al or doughnut-shaped ferrite core. Because of their symmetry, toroidal cores allow a minimum of the magnetic flux to escape outside the core (called ''[[leakage flux]]''), so they radiate less electromagnetic interference than other shapes. Toroidal core coils are manufactured of various materials, primarily ferrite, powdered iron and laminated cores.<ref>{{cite web|url=http://www.vishay.com/docs/34053/definit.pdf |title=Inductor and Magnetic Product Terminology |publisher=Vishay Dale |access-date=2012-09-24}}</ref>