Q4 - A magnetic circuit consisting of three parts in parallel : Part A is of length 80 mm and cross-sectional area 50 mm². Part B is of length 60 mm and cross-sectional area 90 mm². Part C is of length 75 mm and cross-sectional area 60 mm². These parts are made from material having the following corresponding magnetic characteristic values respectively: H = 620 At/m and B=0.9 T, H=500 At/m and B = 0.5 T, H = 800 At/m and B = 0.7 T. If an airgap of 1 mm length is made in part C, calculate the current necessary in a coil of 4000 turns wound on part A to produce an airgap flux density of 0.3 T.
Ampere Circuital Law
Ampere's Law states that "for any closed loop path, the sum of the length elements times the magnetic field in the direction of the length element is equal to the permeability times the electric current enclosed in the loop.”
Current Density
To design the electrical and electronic system, the current density is an important factor. The designer current level is the factor on which the circuit performance depends and with the help of the dimensions of the conducting current the current density is then determined. For instance, despite the lower current demanded by smaller devices as integrated circuits are reduced in size, there is a type of trend in achieving the higher device number in even smaller chip areas. The current density is increased in this region at higher frequencies because the conducting region in a wire becomes confined and this is known as the skin effect. The consequences increase as the current densities become higher.
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