self or mutual induction question..

https://i28.tinypic.com/ng7ny9.jpg
i was told that the two selonoid are mixed with one another.
regarding A:
why they use only one flux

why arent they summing both flux?

regarding C:
why are we find the L of selonoid B
and then do e=-L5

why we use mutual induction here
what is wrong with this way?

i was told that the two selonoid are mixed with one another.
regarding A:
why they use only one flux

why arent they summing both flux?

Click to expand...

Mutual inductance results from the flux through a coil produced by the field from a second coil.

Self inductance results from the flux through a coil produced by the field from the same coil.

The problem states the fluxes produced by the field from coil A in coil A and in coil B respectively.

The flux through coil A gives rise to the self inductance of A and the flux through coil B gives rise to the mutual inductance.

If the example helps, I think that mutual induction takes place in transformers. Transformer - Wikipedia, the free encyclopedia

regarding C
why are we using the mutual induction
why arent we using the self inductance of coil B
??

regarding C
why are we using the mutual induction
why arent we using the self inductance of coil B
??

Click to expand...

Because it asks for the emf in coil B caused by the change in current in coil A (the other coil).

Self inductance relates the emf in a coil caused by a change in current in the same coil.

ok thanks