Editing Curl (mathematics) (section)

===Further examples===
* In a vector field describing the linear velocities of each part of a rotating disk in [[uniform circular motion]], the curl has the same value at all points, and this value turns out to be exactly two times the vectorial [[angular velocity]] of the disk (oriented as usual by the [[right-hand rule]]). More generally, for any flowing mass, the linear velocity vector field at each point of the mass flow has a curl (the [[vorticity]] of the flow at that point) equal to exactly two times the ''local'' vectorial angular velocity of the mass about the point.
* For any solid object subject to an external physical force (such as gravity or the electromagnetic force), one may consider the vector field representing the infinitesimal force-per-unit-volume contributions acting at each of the points of the object. This force field may create a net ''[[torque]]'' on the object about its center of mass, and this torque turns out to be directly proportional and vectorially parallel to the (vector-valued) integral of the ''curl'' of the force field over the whole volume.
* Of the four [[Maxwell's equations]], two—[[Faraday's law of induction|Faraday's law]] and [[Ampère's circuital law|Ampère's law]]—can be compactly expressed using curl. Faraday's law states that the curl of an [[electric field]] is equal to the opposite of the time rate of change of the magnetic field, while Ampère's law relates the curl of the magnetic field to the current and the time rate of change of the electric field.