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

A charged particle (charge q) is moving in a circle of radius R with uniform speed v. The associated magnetic moment $$\mu $$ is given by

Curie temperature above which

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