variation of inductance with frequency Options

[shopitham]

Hai friends,

I am dng a project on measuring inductance using network analyzer. I have few basic questions

1)Why inductance of a coil or inductor should vary with frequency, when it value is constant?
2)Do we have to specify the inductance value at a particular freq ?

This post has been edited by shopitham: Dec 1 2010, 18:06

[pdq]

There can be a lot of reasons why the inductance of an inductor can vary with frequency.

For example, no inductor is purely indictive. Any inductor also has a capacitive element inherent in its construction that acts much like a parallel capacitor. Because of this, the reactance increases with frequency, with simultaneous change in phase angle, until above a certain frequency it acts like a capacitor instead of an inductor.

Were you interested in the audio-frequency range? Because most of this only applies at RF frequencies.

[Woodinville]

There can be a lot of reasons why the inductance of an inductor can vary with frequency.

For example, no inductor is purely indictive. Any inductor also has a capacitive element inherent in its construction that acts much like a parallel capacitor. Because of this, the reactance increases with frequency, with simultaneous change in phase angle, until above a certain frequency it acts like a capacitor instead of an inductor.

Were you interested in the audio-frequency range? Because most of this only applies at RF frequencies.

When magnetic core materials are involved, it's a bit more complicated to say the least, and depends not only on the bulk properties of the core, but also on the physical design, lamination, etc.

[saratoga]

Why inductance of a coil or inductor should vary with frequency, when it value is constant?

Because the material properties of the inductor are themselves a function of frequency.

[shopitham]

There can be a lot of reasons why the inductance of an inductor can vary with frequency.

For example, no inductor is purely indictive. Any inductor also has a capacitive element inherent in its construction that acts much like a parallel capacitor. Because of this, the reactance increases with frequency, with simultaneous change in phase angle, until above a certain frequency it acts like a capacitor instead of an inductor.

Were you interested in the audio-frequency range? Because most of this only applies at RF frequencies.

Not the audio frequency range .A network analyzer can oly measure frequency above 0.3M hz. its oly in the RF range.

can u suggest me some std inductor with which i can try out my experiment ?


Thanks.

[pdq]

can u suggest me some std inductor with which i can try out my experiment ?

Get some enamel insulated copper wire, something around 18 to 22 gauge. Wrap a few turns around a pencil, then strip the enamel off the ends. Calculate its inductance.