I know this is a very broad question, but what would be a decent ball park estimate for resistance (in ohms) in an inductor that would be found in a parts bin at a university. The inductors values range from 2mH to 100mH. But, more specifically, is it over or under 300 ohms?
There is another factor that effects the resistance of an inductor, but it won't effect the inductors you are talking about, its the skin effect. For RF frequencies current is limited to flowing on the surface of a wire. Therefore RF inductors have more resistance at operating frequency than at DC.
It will probably be less than 300 ohms. Varies, but it's just a length of copper wire, it can be as low as less than an ohm. That is a very narrow range of inductors, usual values are in the 10 - 1000 ?H. edit: A little research turns up an audio inductor of 100mH that has 1000 ohms DC resistance, so higher resistance is possible. .
There are (2) types of resistance for an inductor: 1. DC Resistance 2. AC Resistance The equation is R + j X A 2 mH inductor will be 300 ohms (of Reactance jX) at 300 X / 2 * pi freq * L 23,873.2415 Hertz This is with ZERO DC resistance (R). A 100 mH inductor will be 300 ohms (of Reactance jX) at 300 X / 2 * pi freq * L 477.4648 Hertz This is with ZERO DC resistance (R). Notice that the resistance starts at a lower frequency for larger inductors ! For all inductors; the resistance will go up with frequency for an inductor as the frequency is DIRECTLY PROPORTIONAL to INDUCTIVE REACTANCE. If you had some small DC resistance, such as 5 ohms, the frequency would be even lower before it hits 300 ohms. Generally larger wire inductors will have lower DC resistance.
Inductors are not supposed to have resistance. They are supposed to be pure REACTORS to the signal, and not resistors. They are suppose to act exclusively on the rate of change of current, and not on the current itself. Resistance of an inductor is parasitic. It is simply there due to the fact that it is a long wire, and usually less than ten ohms.
