If you have a length (l) of wire coiled to make an inductor and you stretch the wire (ie. space the coils further) but do not change the diameter (see attached .bmp) is the inductance the same? I understand inductance to be L = (mu N^2 A) / l + 0.45d. So if I'm stretching the coils but not changing l (length) will the inductance change? I guess that technically the cross sectional area (A) would be changing slightly due to stretching to coils ... but I'm not sure if that minor variation is negligible - since I'm not actually changing the diameter. I thought that you compress/decompress coils (which is what I think this example is) to tune inductance... is this what's happening? How does a variable inductor work? I have no equipment so I can't just coil some wire and stretch it myself to see. Insight is appreciated. Thanks.
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