Inductor

A magnetic field is set up around the conductor as concentric circles.
If a coil of wire has a current flowing through it, the magnetic flux due to each turn will link with every other turn and produce the same sort of magnetic field as a permanent magnet. Such a coil is called a solenoid as shown here. It acts as a magnet only when current is flowing through it.
The magnetic polarity of the solenoid can be determined from the direction of current flow as seen looking in the ends, as shown in the diagram. From that the direction in which the magnetic field is acting can also be found.
Solenoids or electro­magnets are widely used in electronic equipment. Loudspeakers, headphones, moving coil microphones, measuring instruments, transformers and such things, depend on electromagnetism for their operation.
A inductor may be air-cored or have a solid core.