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Name:  Richard
Status:  student
Age:  30s
Location: N/A
Country: N/A
Date: 2000-2001


Question:
At what frequency do inductors fail to pass an a.c. signal?


Replies:
Richard,

There is no frequency at which they start or stop. How well a particular inductor works in an AC circuit depends on the rest of the circuit as much as it depends on the inductor.

A particular inductor, with inductance L, responds to the rate at which the current passing through it changes. The faster the current changes, the more voltage is used by the inductor. In a circuit, an inductor limits the rate at which the current can change. For an AC signal, the "inductive reactance" of an inductor is 2(pi)fL: the product of 2*pi*frequency*inductance. This is the ratio of peak voltage across the inductor to peak current through the inductor. Greater frequency means less current. This is because greater frequency means the current changes more quickly. Still, there is no real maximum frequency.

Dr. Ken Mellendorf



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