Electrical Machine I

A circular ring of magnetic material has a mean length of $0.8\ \text{m}$, cross sectional area of $120\ \text{cm}^2$, and an air gap of $5\ \text{mm}$. Calculate the magnetizing current required to produce a flux of $1\ \text{mWb}$ in the air gap if the ring is wound uniformly with a coil of 220 turns. Take relative permeability of the ring material $= 500$ and neglect leakage and fringing.