# Inductor values and inductor cores.

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#### nguyennam

Hi everybody,

As far as I know, the inductance of an inductor is dependent on the frequency, but in most cases, I see an inductor in any circuit in any literature shown with its inductance value, but no frequency specified.

So could you kindly let me know inductor value shown in any circuit could be defined at which frequency, any standard about this matter?

On the other hand, in some circuits, inductors have core of EE, or O, U shapes, which mean closed magnetic circuit, while in another circuits, inductors have core of bar-type which means opened magnetic circuit.

I also would like you to let me know the differences between 2 types of inductors using those types of cores. And when do we use this type, not that type??

Thank you very much in advance.

nguyennam

#### sohiltri

##### Member level 5
As far as i know inductance does not depends on freq,only the reactance shown to the circuit depends on freq. ...

X=Lω=2ΠfL

inductance value depends on number of turns and it diameter and not on freq...

i think i have made it cleared ...jus correct me if i am wrong

regards,
sohil

#### nguyennam

Sohiltri,
Yes, reactance of a inductor/capacitor is a function of frequency and inductance/capacitance.

However, only inductor with air core has "fixed" inductance, any inductor with magnetic core has its inductance which varies significantly when frequency changes.

nguyennam

#### siongboon

Inductance is found on the wire turns.
The impedance across the inductor changes
with frequency, not the inductor value.
Inductor value is fixed, regardless of frequency.

Those ferrite core with U, O, etc shapes
are used to enhance the inductances.

Maybe you might like to find out more in the internet.

Hope that you got the idea now.

www.siongboon.com

##### Member level 1
Dear nguyennam,

The inductance L is normally constant whether in dc or ac circuits. However, in ac circuits, the inductive reactance of the inductor L is equivalent to ωL while ω=2Πf. Hence, the indcutive reactance is dependent on f.

Thanks nguyennam.