Duduli

Answer:-  The alternate magnetisation and demagnetisation of the iron core of transformer results the lag of magnetism of iron core therefore more energy is loss occur in transformer that loss is called Hysterisis loss.

Answer:- The temperature below which a magnetic material behave like a ferromagnetic material and above which it behaves like a paramagnetic material is called Curie temperature of that material.           For Iron = 770⁰C           For Nickel = 358⁰C