Nickel shows ferromagnetic property at room temperature. If the temperature is increased beyond Curie temperature, then it will show

Curie temperature above which

If the magnetic dipole moment of an atom of diamagnetic material, paramagnetic material and ferromagnetic material are denoted by $$\mu $$_d, $$\mu $$_p and $$\mu $$_f respectively, then

A coil in the shape of an equilateral triangle of side $$l$$ is suspended between the pole pieces of a permanent magnet such that $$\overrightarrow B $$ is in plane of the coil. If due to a current i in the triangle a torque $$\tau $$ acts on it, the side $$l$$ of the triangle is