Solenoid (physics)

A solenoid. The direct current i enters at the left and travels around the cylinder through the conducting wire. Two magnetic field lines are shown in blue. The magnetic induction B is a vector field tangent to field lines. The direction of B and i are connected via the right screw rule.

In physics, a solenoid is a spiral of insulating wire wound around a cylinder. When a direct current passes through the wire a magnetic field is generated. Usually the cylinder is made of iron or other ferromagnetic material that enhances the magnetic field.