Why does reversing primary and secondary coils not change mutual inductance?

[songoku]

Homework Statement

A mutual inductor consists of two coils X and Y arranged so that one quarter of the magnetic flux produced by X links with Y. When X is used as the primary coil and Y as the secondary, the mutual inductance is M. What is the mutual inductance when Y is used as primary coil and X as the secondary?

a. M/4
b. M/2
c. M
d. 2M
e. 4M

Homework Equations

$$E=-M\frac{\Delta I}{\Delta t}$$

The Attempt at a Solution

I think the answer is (c) because M is independent whether X or Y is the primary one. Am I right?

Thanks

 

[rl.bhat]

Yes. M12 = M21