Q$\mathrm{.}3/(3)$ Marks

D$.$C Machine has $2p=4$ the external diameter of yoke is $110$ cm $,$ the internal diameter of yoke is $90$ cm $.$ the length of the pole is $37$ cm the width of the pole is $18$ cm $,$ pole arc is $24$ cm the diameter of the armature is $52$ cm the internal diameter of the core is $25$ cm the tooth length is $3\mathrm{.}5$ cm $,$ the width of the slot is $1$ cm the no$.$ of the teeth is $50$ the axial length of the yoke is $40$ cm the axial length of the pole and armature is $35$ cm the useful flux is $90$ mwb the relative permeability for the the yoke is $50$ and for the pole is $1000$ and for core is $3250.$ Determine the m$.$m$.$f for the core.