can the inductor and resistor values be found from the impedance

Question

If the inductive impedance is given can the separate resistor and inductor values be calculated?

OK

The question gives the voltage supply (magnitude and frequency), power factor and current. It also states that the circuit is inductive as the current passes through a single coil.

To satisfy the question the inductor and resistor values are required. Can this be calculated with the information given?

I can find the impedance as a phasor quality using the V/I cos^-1(p.f), but cannot expand this into the separate values for the resistance and inductor.

I don't think its possible and wanted to know if it is possible from more experienced people.

Thanks

Danny

Answer 1

Yes, it's possible, but first you need to choose a model of the device under test, usually one of the below. The exact wording of the question will probably tell you which model you need to use, but the one on the left is much more common. It's the one used to model a real inductor with some resistance in the windings.

^{simulate this circuit – Schematic created using CircuitLab}

You can calculate the complex impedance of either one of those circuit models from first principles using the equations for the resistance of a resistor and the reactance of an inductor. You can convert the impedance you've got from amplitude and phase to complex form. Then you equate these two impedances, separate the real and imaginary parts, and solve for R and L.