<Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> In vector calculus, the curl is a vector operator that describes the infinitesimal rotation of a vector field in three - dimensional Euclidean space . At every point in the field, the curl of that point is represented by a vector . The attributes of this vector (length and direction) characterize the rotation at that point . </P> <P> The direction of the curl is the axis of rotation, as determined by the right - hand rule, and the magnitude of the curl is the magnitude of rotation . If the vector field represents the flow velocity of a moving fluid, then the curl is the circulation density of the fluid . A vector field whose curl is zero is called irrotational . The curl is a form of differentiation for vector fields . The corresponding form of the fundamental theorem of calculus is Stokes' theorem, which relates the surface integral of the curl of a vector field to the line integral of the vector field around the boundary curve . </P>

What is the curl test for vector fields
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