# Homework Help: Complex Power, calc load impedance

1. Nov 30, 2012

### Zarathuztra

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

A load absorbs 58959W at a lagging power factor of pf = 0.73. If the current flowing through the load is ix = 0.001A-rms , determine the impedance of the load.

2. Relevant equations

Ohms law
Impedance/Voltage/Power Triangles

3. The attempt at a solution
If the load absorbs 58959W, I'm assuming that is apparent power (S)

If 58959W is S then by Pavg = S*pf = Irms2R

R = 58959*.73/.0012 = 43.04 GΩ (must be wrong...)

I would then take R/pf = Z... but the number gets more ridiculous. How am I going about this wrong?

2. Nov 30, 2012

### Staff: Mentor

Apparent power is usually specified in VA rather than W. Real power is given in W, reactive power in VAR.

3. Nov 30, 2012

### Zarathuztra

then 58959 = Pavg

and Pavg = irms2 * R

so 58959/.0012 = R = 5.9 * 1010

Z = R/pf = 5.9 * 1010 / 0.73

4. Nov 30, 2012

### Staff: Mentor

Okay, but usually an impedance is specified by its real and reactive components (it's actually a complex number), or in magnitude and angle form.

5. Nov 30, 2012

### Zarathuztra

ah that's what was wrong with my input.. lol. Thanks gneill