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[student 13]

circular coil placed vertically such that its axis is in the same direction of the earth's magnetic field if the coil rotates 180 the magnetic flux density become the double . calculate the magnetic flux density at the center due to current .. the earth's magnetic flux density = 0.3 T




two concentric circular coil in same plane the diameter of the first is twice the second . when the current in the two coils have the same direction we find that B1 in the outer circle is less than B2 of the inner coil but when the current direction is reversed in the first outer coil the magnetic flux density decreases in the center to half its value .. calculate ratio bet their no of turns