An electromagnet has a magnetic circuit that can be regarded as comprising three parts in series of a uniform cross-sectional area: Part a is of length 100 mm and cross area 50 mm². Part b is of length 50 mm and cross area 70 mm², Part c is an air-gap of length 0.5 mm and cross area 150 mm². Parts a and b are made from a material haying the following corresponding Magnetic characteristic values: H= 620 Avm; B= 0.9 T H=275 Aum; b=0.5 T Determine the current necessary in a coil of 4000 turns wound on part b to Produce an air-gap flux density of 0.3 T.

An electromagnet has a magnetic circuit that can be regarded as comprising three parts in series of a uniform cross-sectional area: Part a is of length 100 mm and cross area 50 mm². Part b is of length 50 mm and cross area 70 mm², Part c is an air-gap of length 0.5 mm and cross area 150 mm². Parts a and b are made from a material haying the following corresponding Magnetic characteristic values: H= 620 Avm; B= 0.9 T H=275 Aum; b=0.5 T Determine the current necessary in a coil of 4000 turns wound on part b to Produce an air-gap flux density of 0.3 T.