# Apparent power, impedance and alternating current.

1. Apr 21, 2013

### 0fibonacci1

1. The problem statement, all variables and given/known data
Two serially connected impedances one with $\Phi$ = π/3 and other with $\Phi$ = 0. They have apparent power of S1=S2=200VA. Find total apparent power.

2. Relevant equations

S = sqrt(P^2 + Q^2)

3. The attempt at a solution

so cosPhi = P1/S1. So P1=cosπ/3*200=100W. For other one P2 = cos0*200=200W. How should I continue? Should I find Q too and derive somehow a equation to sum those powers?

2. Apr 21, 2013

### milesyoung

The complex power, S, delivered to the load is:
S = S1 + S2

and the angle between S1 and S2 is the same as the angle between the impedances.

You want to find the apparent power |S| = |S1 + S2|. If, say:
S1 = 200∠0
S2 = 200∠π/3

Try drawing them in the complex plane. The length of their sum is the answer you're after.