The attached example was scanned from a textbook. I tried to calculate S1 but the answer I got was different from the one shown in text. Could someone please help me to verify whether the solution provided in the text is CORRECT or WRONG?

My calculation:

I
= (V1 - V2) / Z
= (240 - 208 - j120) / j10
= -12-j3.2

S1
= V1 x (-I*)
= 240 x (12-j3.2)
= 2880-j768

Question: Why a negative '-' sign in front of I* is required for the calculation of S1? Pls advise.


S2
= V2 x (I*)
= (208+j120) X (-12+j3.2)
= -2880-j774.4

 

Hi

The asterick indicates a footnote for the -I. What does the footnote say? The negative sign usually indicates that I is flowing in the opposite direction of that assumed in the diagram.

John