# can the inductor and resistor values be found from the impedance

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

• Only if you have the phasor and frequency. Commented May 8, 2016 at 11:37
• the supply frequency is a given. Also the inductive impedance is expressed as a phasor quantity with the angle Commented May 8, 2016 at 11:41
• I can only reduce the expression to: Commented May 8, 2016 at 11:44
• Danny, put all the info in the question. Don't sprinkle it through the comments. Commented May 8, 2016 at 11:45

## 1 Answer

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.

• Thanks but I don't have the resistor or inductor values. I only have the impedance value as a phasor / vector quantity Commented May 8, 2016 at 11:53
• Yes, when you pick a model and calculate the complex impedance you will get an equation containing two unknowns, L and R. Then, when you set that equal to the impedance you have, you'll be able to work out what they are. Commented May 8, 2016 at 11:55
• OK I will add that to the question the model is for a single coil so series. Commented May 8, 2016 at 11:58