# Homework Help: Energy stored in the magnetic field of two inductors

1. Jul 23, 2008

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1. The problem statement, all variables and given/known data
Two solenoids on the same cylindrical axis
Solenoid A has 400 loops and a current of 3,5 amp. Produces a flux of 300microWb on itself and 90 microWb on solenoid B
Solenoid B has 700 loops

2. Relevant equations
Calculate the energy stored in the system.

3. The attempt at a solution
Well, I know that the energy stored in magnetic field equals the square of the field over two times mu zero, but that's not the case here since I don't have the field.
I also know that for a self-inductor the energy stored equals to the square of the current times the self induction over two.
I believe I need to use that last equation, but as I don't understand where it comes from I don't know what to put as self-induction, or if it works also when the induction is produced by another coil.

2. Jul 23, 2008

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Did I do something wrong here not to get any answer?