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Two (insulated) coils are wound, (one over the other), on a solenoid core. If the number of turns, per unit length, of the first coil and of the second coil, were to be increased by a factors of 3 and 4, respectively, the self inductance of the two coils (L1 and L2) and their mutual inductance (M), would increase (respectively) by factors of (1) 3, 4 and 12 (2) 3, 4 and 4/3 (3) 9, 16 and 16/9 (4) 9, 16 and 12

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