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Unformatted text preview: Test # 2 Solutions 1. By what distance must two currents of +330 A each be separated so that the force per unit length between them is 10- 2 N/m ? In order for this force per unit length to be repulsive, how should the two currents be owing? Solution: We have F l = 2 k I 1 I 2 r r = 2 k I 1 I 2 1 ( F/l ) = (2 10- 7 330 330 10 2 ) m = 2 . 178 m The two currents should be owing anti-parallel to each other (parallel but op- posite in direction). 2. A coil with 250 loops of conducting wire is subject to a magnetic field that went from 0 T to 1 T in 0 . 1 s The cross sectional area of the coil is 5 cm 2 . What is the change of the electric potential induced by the changing magnetic field? In words, what can you say about the direction of the current induced in the loops? Solution: Assuming the magnetic field is perpendicular to the face of the coil (other- wise we would have to account for the angle between the face and the magnetic field), we have =...
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