Finding complex power in AC circuit

[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?

 

[Chandra Prayaga]

Is this a homework problem?

 

[Raghav Gupta]

Is this a homework problem?

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?

 

[Henryk]

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