The magnet fitted to coils is often used to affect the core saturation characteristics, and with a rising current through the winding the direction of current flow would be critical in the design application.

 

Hello,

The longer and shorter wires could also indicate the start and the end of the coil.
Basicaly it would not make any difference in use.

Bertus

 

Hello,

The longer and shorter wires could also indicate the start and the end of the coil.
Basicaly it would not make any difference in use.

Bertus

I was under the same impression. Until it was mentioned that the direction of the magnetic field could affect the components that surrounded the inductor.

 

Hello,

When the coil is used as inductive coupling device, it could indeed make a differende wich way it is connected.

Bertus

 

Hello,

When the coil is used as inductive coupling device, it could indeed make a differende wich way it is connected.

Bertus

Also, when you don't want any inductive coupling, orientation is important.

 

The question I wonder about is, even if you know which way the coil (and its field) is oriented, and you care about interference with other nearby inductors, then what? Other than testing A vs B like an optometrist, I don't see how you could use the information.

 

The question I wonder about is, even if you know which way the coil (and its field) is oriented, and you care about interference with other nearby inductors, then what? Other than testing A vs B like an optometrist, I don't see how you could use the information.

Inductors are known to "talk" to each other. To mitigate this, you use shields (notice that this inductor is unshielded), placement (move affected circuits away from each other) and orientation. Inductor "communication" is minimal when they are orthogonal to each other.

 

I would sincerely like to see an application in a PCB where the orientation of the inductor's field is considered important. Other than for its being used as an electromagnet, of course.

In the very early days of TRF radios, up to 3 inductors were all mounted 90 degrees to each other to minimise coupling and consequent RF feedback. Any more than 3 required screened compartments or large physical separation.

 

I have a flying toy with an electric compass on board to help with navigation. I imagine any near by inductors would affect the readings and need to be accounted for, making their polarity important. Maybe someone with more knowledge on the subject than me can correct me if I'm wrong.

 

Bertus, SLK001 and RecklessRog are correct, A company I once worked at we had a circuit that used a coil like the one shown. If the coil was installed wrong (leads reversed) the circuit would not work.

 

Bertus, SLK001 and RecklessRog are correct, A company I once worked at we had a circuit that used a coil like the one shown. If the coil was installed wrong (leads reversed) the circuit would not work.

What kind of circuit was it?

 

It's odd that, if it matters so much, Bourns makes no note of what the longer lead indicates.

 

I have a flying toy with an electric compass on board to help with navigation. I imagine any near by inductors would affect the readings and need to be accounted for, making their polarity important. Maybe someone with more knowledge on the subject than me can correct me if I'm wrong.

Some electronic magnetic compasses have a calibration mode to cancel out nearby magnetic fields or materials such as a car dashboard.

 

What kind of circuit was it?

It was an oscillator circuit that used 2 of those type of coils with the flat tops facing each other with an air gap. So they actually made an air gapped transformer. Of course if one of the coils was installed backwards the phase would be wrong and it would not oscillate. The coils were mounted in a plastic housing with about a 1/8 inch gap between them, there was a small ridge formed on one side of the plastic that formed a ramp. When a coin rolled down this ramp as it passed between the two coils the amplitude of the oscillator would change in proportion to the metal content of the coin.