1). A ring of outer diameter 80 cm is made from square of cross -section steel bar size(8 *8 cm) . If relative permeability 1200 for steel . calculate the current needed to produce the flux of 4 mili weber in the steel . In a coil of 600 turns wound on the core .what is the flux density and magnetizing force H?

2)  A rectangular transformer core is made with silicon steel with area 30 cm square and mean length 1.25 metre and air gap of 8 mm is cut on the core .Given that leakage co-efficient is 1.25 and relative  permeability is 1500.Caculate the number of turns needed in the exisisting coil which carries a current of 3 ampere to produce a flux density 1.5 tesla in a airgap?