Toroidal inductors and transformers
![Several small toroidal inductors. The major scale is in inches.A small toroidal transformer.](/Images/godic/202502/17/Small_Toroidal_Inductors4700.jpg")
![A small toroidal transformer.](/Images/godic/202502/17/Small_toroidal_transformer4700.jpg")
![Fig. 1. Coordinate system. The Z axis is the nominal axis of symmetry. The X axis chosen arbitrarily to line up with the starting point of the winding. ρ is called the radial direction. θ is called the circumferential direction.](/Images/godic/202502/17/Toroidal_Inductor-Simple_with_Axes4700.JPG")
![Fig. 2. An axially symmetric toroidal inductor with no circumferential current.](/Images/godic/202502/17/Toroidal_Inductor-with_Fully_Confined_Magnetic_B_Field,_Three_View4700.JPG")
Toroidal inductors and transformers are passive electronic components, typically consisting of a circular ring-shaped magnetic core of high magnetic permeability material such as iron powder or ferrite, around which wire is coiled to make an inductor. Toroidal coils are used in a broad range of applications in AC electronic circuits, such as high-frequency coils and transformers.