49. (a) The magnitude of the magnetic dipole moment is given by µ = NiA ,whe re N is the number of turns, i is the current in each turn, and A is the area of a loop. In this case the loops are circular, so A = πr 2 ,where r is the radius of a turn. Thus i = µ Nπr 2 = 2 . 30A · m 2 (160)( π )(0 . 0190 m) 2 =12 .
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