Electrical Machine

Define the term magneto motive force and magnetizing force for magnetic circuit. A ring has mean diameter of 21 cm and a cross sectional area of 10 cm². The ring is made up of semicircular section of cast iron and cast steel, with each joint having a reluctance equal to an air gap of 0.2 mm. Find the ampere turns required to produce a flux of 0.8 mWb. The relative permeability of cast steel and cast iron are 800 and 166 respectively.