# Finding complex power in AC circuit

1. Oct 31, 2015

### Raghav Gupta

In a branch I have to find complex power which is having current 19.41<-37.3 A and impedance 4+j3 Ω
What I used is i2z and I was getting 1489.85 - j1152.74 W.
This is wrong but I don't know how because by this site the answer was different
http://www.rapidtables.com/calc/electric/power-calculator.htm
Can someone tell me what is wrong going on?

2. Oct 31, 2015

### Chandra Prayaga

Is this a homework problem?

3. Oct 31, 2015

### Raghav Gupta

No the homework problem was something other. When I was doing it in middle this query araised. I just want to ask the concept that when impedance is given and current is given, the complex power should be Vi or i2z, isn't it?

4. Nov 1, 2015

### Henryk

The voltage is give as $V = I * Z = I * Re(Z) + I * Im (Z)$. The second term is 90 degrees out of phase with respect to current. The average power dissipated is then $I_{RMS}^2 * Re(Z)$