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Why would the legs on a radial through hole inductor be different lengths from eash other? There is no polarity to indicate like a LED or Electrolytic cap...

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    \$\begingroup\$ Are they different lengths? Most of the ones I've seen are the same length. \$\endgroup\$ – Hearth Apr 26 '19 at 20:56
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    \$\begingroup\$ A specific example will help... ok found one: farnell.com/datasheets/… \$\endgroup\$ – Eugene Sh. Apr 26 '19 at 20:58
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    \$\begingroup\$ There will be some difference in the external field, for example. \$\endgroup\$ – Spehro Pefhany Apr 26 '19 at 21:06
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    \$\begingroup\$ Easier to insert into a pcb \$\endgroup\$ – Chu Apr 26 '19 at 21:10
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Sometimes the properties are a bit different depending on mounting direction. From the murata website (https://www.murata.com/en-us/products/emiconfun/inductor/2012/05/14/en-20120514-p1):

If the inductor structure is not perfectly symmetric, properties will change with the mounting direction. We therefore leave a mark so that the user will know the inductor has directionality. That way, when they use the inductor, they can hope to make the fullest use of the intended properties.


Also it can be useful to know the polarity to understand the direction of the magnetic field that will be induced. If a lot of inductors are used close to each other, their fields will interact.

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  • \$\begingroup\$ The link is for surface mount which I can understand, but this is a radial through hole bobbin. \$\endgroup\$ – SamR Apr 26 '19 at 21:17
  • \$\begingroup\$ What is "this" which you are referring too. Please be so kind as to post a link to the datasheet, or at least a picture. Until then, -1 to the question. \$\endgroup\$ – Nick Alexeev Apr 26 '19 at 21:44
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The answer is that the long leg indicates the bottom of the vertical coil. When I placed them in a Hartley oscillator the legs had to both be in the same orientation for it to work. Something new for me so lesson learned and filed for future use.

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