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.

How inductor work

An inductor is about as simple as an electronic component can get -- it is simply a coil of wire. It turns out, however, that a coil of wire can do some very interesting things because of the magnetic properties of a coil.

Magnetic materials

Magnetic materials in common use for the cores of solenoids are:

Soft iron
Easy to magnetise and demagnetise. Used for motor pole-pieces.

Silicon iron
used for transformer laminations and AC motors. Low-loss.

Nickel iron alloy
Also known as radio metal and mu-metal, is used for high-class audio transformers and cathode-ray tube screens.

Ferrites
Iron oxide based materials used for a wide range of applications in radio and electronics generally. The characteristics depend on the mix of materials in the core and is extremely varied. Also known as ferroxdure and ferroxcube.