  Within the framework of continuum theory, we draw a parallel between
ferromagnetic materials and nematic liquid crystals confined on curved
surfaces, which are both characterized by local interaction and anchoring
potentials. We show that the extrinsic curvature of the shell combined with the
out-of-plane component of the director field gives rise to chirality effects.
This interplay produces an effective energy term reminiscent of the chiral term
in cholesteric liquid crystals, with the curvature tensor acting as a sort of
anisotropic helicity. We discuss also how the different nature of the order
parameter, a vector in ferromagnets and a tensor in nematics, yields different
textures on surfaces with the same topology as the sphere. In particular, we
show that the extrinsic curvature governs the ground state configuration on a
nematic spherical shell, favouring two antipodal disclinations of charge +1 on
small particles and four $+1/2$ disclinations of charge located at the vertices
of a square inscribed in a great circle on larger particles.
