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## Homework Statement

Coil 1 has L=25mH and N=100 turns. Coil 2 has L=40mH and N=200. The coils are rigidly positioned with respect to each other, and their mutual inductance is 3.0mH. A 6.0mA current in coil 1 is changing at 4.0 A/s. (a)What magnetic flux Phi12 links coil 1 to coil 2, and what is the self-induced emf that appears in coil 1? (b) What magnetic flux Phi21 links coil 2 to coil 1, and what is the mutually induced emf that appears in coild 2?

## Homework Equations

I know I need E=-L(dI/dt) for the self induced emf and E=-M(dI/dt) for the emf induced in coil2.

## The Attempt at a Solution

Solving for both emfs easy and I understand it. What I don't get is what is ment by the magnetic flux that links coil 1 to coil 2 and visea-versa. Would Phi12=L1I1+MI2 and Phi21=L2I2+MI1?

Given that I dont have length (but since I do have number of total turns and would assume that I can assume a length of 1m?) or cross-sectional area, I dont see how you could ever calculate the induced current. I think I have a conceptual problem here and my book is sort of famous for this. Anyone?