# Phase Angle between Voltage and Current

1. Oct 30, 2013

### theintarnets

1. The problem statement, all variables and given/known data

"When only a resistor is connected across the terminals of an ac generator (111 V) that has a fixed frequency, there is a current of 0.465 A in the resistor. When only an inductor is connected across the terminals of this same generator, there is a current of 0.360 A in the inductor. When both the resistor and the inductor are connected in series between the terminals of this generator, calculate the following.
(a) the impedance of the series combination

(b) the phase angle between the current and the voltage of the generator"

I got the impedance to be 389.94, but I don't know what other formulas to use to get the phase angle. Specifically, I don't know how to find XL.

2. Relevant equations

Phase angle = arctan(XL/R)

2. Oct 30, 2013

### theintarnets

Nvm, I found another formula for phase angle = cos(R/Z)

I had the wrong variables written into the equation of Z, so I didn't realize I already calculated XL >.<

Last edited: Oct 30, 2013
3. Oct 30, 2013

### barryj

I don't know how to find XL.

How would you find R? It is similar.

4. Oct 31, 2013

### Staff: Mentor

phase angle ɸ = cos⁻¹ (R/Z)

this is identical with ɸ = tan⁻¹ (X/R)

5. Oct 31, 2013

### Staff: Mentor

Ohm's Law, you know the applied voltage and you know the current that flows.