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Does anyone know what the Al value given in the datasheets means when choosing cores?

There is no explanation of the subject other than the formula anywhere. And why is (n^2) / equal to L? Why do we square n?

sezi
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    Does this answer your question? [Why is inductance (L) proportional with turns-square (N²)?](https://electronics.stackexchange.com/questions/109887/why-is-inductance-l-proportional-with-turns-square-n%c2%b2/109894#109894) – Andy aka Jun 01 '22 at 18:17
  • [Permeance and \$A_L\$](https://e-magnetica.pl/al_value). – Andy aka Jun 01 '22 at 18:23

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Inductor basic equations: -

$$V = N\dfrac{d\Phi}{dt} = L\dfrac{di}{dt}$$

Hence, \$N\Phi = Li\$

And, because \$\Phi\$ is flux density × Area we can say: -

$$L = \dfrac{NBA}{i} = \dfrac{N^2 BA}{Ni}$$

Ampere turns are H (magnetic field strength) multiplied by effective core length, \$\ell\$ so....

$$L=\dfrac{N^2 BA}{H\ell}$$

And because \$B/H = \mu\$, we can say: -

$$\dfrac{N^2 \mu HA}{H\ell} = \dfrac{N^2 \mu A}{\ell}$$

Inductance is proportional to turns squared.

Andy aka
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