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A '''solenoid''' is a useful device that generates a nearly uniform [[magnetic field]], similar to that of a [[bar magnet]], from an [[electrical current]].<ref>[https://www.britannica.com/science/solenoid-electronics Solenoid] from britannica.com</ref> It consists of a tightly-wound coil of wire to generate a magnetic field along the axis of the coil. Their length tends to be much greater than their [[diameter]]. The word solenoid can also refer to a specific [[electromagnetism|electromagnetic]] device that creates motion when an electrical current is applied.<ref name=britannica>[https://www.britannica.com/science/electromagnet#ref244719 Electromagnet] from britannica.com</ref> Often this motion is in the form of an [[iron]] plunger that moves in and out.

A '''solenoid''' is a useful device that generates a nearly uniform [[magnetic field]], similar to that of a [[bar magnet]], from an [[electrical current]].<ref>[https://www.britannica.com/science/solenoid-electronics Solenoid] from britannica.com</ref> It consists of a tightly-wound coil of wire to generate a magnetic field along the axis of the coil. Their length tends to be much greater than their [[diameter]]. The word solenoid can also refer to a specific [[electromagnetism|electromagnetic]] device that creates motion when an electrical current is applied.<ref name=britannica>[https://www.britannica.com/science/electromagnet#ref244719 Electromagnet] from britannica.com</ref> Often this motion is in the form of an [[iron]] plunger that moves in and out.

A solenoid can be very useful as the [[magnetic field]] it produces along its axis is uniform.<ref name=hyperphysics>[http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/solenoid.html Solenoid] from hyperphysics.phy-astr.gsu.edu</ref> Its overall magnetic if is very similar to that of a [[bar magnet]]. Its field can be strengthened by placing a ferromagnetic core composed of [[iron]] or [[steel]]. These contain magnetic domains, which act like tiny magnets and all align when put in an external magnetic field, increasing the overall field.

A solenoid can be very useful as the [[magnetic field]] it produces along its axis is uniform.<ref name=hyperphysics>[http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/solenoid.html Solenoid] from hyperphysics.phy-astr.gsu.edu</ref> Its overall magnetic if is very similar to that of a [[bar magnet]]. Its field can be strengthened by placing a ferromagnetic core composed of [[iron]] or [[steel]]. These contain magnetic domains, which act like tiny magnets and all align when put in an external magnetic field, increasing the overall field.

The field within the solenoid tends to be very uniform, while the surrounding field is normally extremely weak.<ref name=hyperphysics/> The field, ''B'', at the center of a solenoid is given by:<ref name=hyperphysics/>

The field within the solenoid tends to be very uniform ([[field lines]] are uniformly spread), while the surrounding field is normally extremely weak.<ref name=hyperphysics/> The field, ''B'', at the center of a solenoid is given by:<ref name=hyperphysics/>

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