A radio frequency choke is air cored whereas an audio frequency
Reactance of an inductor, XL = ω L = 2πf (μoμrn2lA)
Using the above expression,
For radio frequency (high frequency) the reactance will be large even for μr =1. That is why radio frequency choke is air cored.
For audio frequency (low frequency) the reactance will be small if μr =1. So to increase the reactance an iron core is inserted (μr is large) that is why the audio frequency choke is iron cored.
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