Determining the constants R and L of a coil

[viciado123]

We determined the constants R and L of a coil by placing it in series with a standard resistor of 10 ohms and reading the voltages on the terminals of Rs, the coil and the series circuit complete. What are the values of R and L for the following voltage readings at 60 Hz:
Vrs = 20; Vcoil = 22,4; Vt = 36

Answer:
R = 5 ohms
L = 26,5mH

I find the current
Vrs = I . Zr
20 = I . 10 I = 2A
Now I do not know how to find R and L

 

[cartonn30gel]

Is this an experiment you've done? Do you have a circuit diagram for this? I'm curious because those voltages don't agree with each other. (if they are measured at the same time, and the circuit is what I think it is)

A diagram is almost a necessity for any circuit question since a small change might significantly alter how current and voltage behave.

 

[cartonn30gel]

Is this an experiment you've done? Do you have a circuit diagram for this? I'm curious because those voltages don't agree with each other. (if they are measured at the same time, and the circuit is what I think it is)

A diagram is almost a necessity for any circuit question since a small change might significantly alter how current and voltage behave.

 

[ehild]

I find the current
Vrs = I . Zr
20 = I . 10 I = 2A
Now I do not know how to find R and L

The current is OK. You know that in Ac circuits, the voltage is impedance times current.
Usually the ohmic resistance of a coil can not be ignored, so you need to treat the coil as an ideal inductor with impedance wL and resistor R in series.

This resistance of the coil adds to the resistance of the total circuit,
too.

Do you know how to calculate the resultant impedance of an inductor L and a resistor R connected in series?

ehild

 

[cartonn30gel]

All right, I get it now. The question should mention that those are the AC peak voltages. You should use phasor magnitudes in your calculations. So they aren't measured at the same time.

 

[ehild]

All right, I get it now. The question should mention that those are the AC peak voltages.

Or rather RMS voltages. The AC voltmeters read the RMS voltage usually.

ehild