General: Minimize Mutual Inductance

How should the winding axes of two solenoid inductors be oriented to minimize their mutual inductance? [G6A19]

A. In line
B. Parallel to each other
C. At right angles to each other
D. Interleaved

The best way to answer this is to imagine the magnetic field lines coming off of a device, much like in the image above.  If you wanted one coil or solenoid to experience the magnetic field from the other, you would line it up with the field lines.  If you did this, you’d have the two inductors sitting parallel to each other.  This is essentially a transformer, and its definitely not what we want.

In order to achieve the opposite effect, you’d simply rotate the second inductor 90 degrees, so that it is perpendicular to the magnetic field.  The answer is C. At right angles to each other.

(image credit: https://commons.wikimedia.org/wiki/File:Solenoid-6.jpg)

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