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
S2
= V2 x (I*)
= (208+j120) X (-12+j3.2)
= -2880-j774.4
In the text, the current is wrong; it should be +12-j3.2. Because of the current error, the value for S2 has the wrong sign but the numbers are correct. The value for S1 is wrong, I don't know how it was calculated.
Your calculation for S1 is correct. In the calculation for S2, you used (-12+j3.2) for the current which is not correct, otherwise you would have got the correct result.
In the text, the author add a '-' sign in front of I for the calculation of S1. Why did the author do so? Thanks.
Russlk said:
In the text, the current is wrong; it should be +12-j3.2. Because of the current error, the value for S2 has the wrong sign but the numbers are correct. The value for S1 is wrong, I don't know how it was calculated.
Your calculation for S1 is correct. In the calculation for S2, you used (-12+j3.2) for the current which is not correct, otherwise you would have got the correct result.
Actually j is not an impossible math function. It is possible to calculate the nth roots of unity (and nth roots of -1 if you wish). Its actually very interesting how sqrt(-1) falls out of the math.
Actually j is not an impossible math function. It is possible to calculate the nth roots of unity (and nth roots of -1 if you wish). Its actually very interesting how sqrt(-1) falls out of the math.
In that case perhaps you would care to show us the answer?.
I was certainly always taught that it's an impossible function, and the technique in using it was to have two of them that cancelled out (mind you, I'm going back a LONG time).
Still, I'll be interested to see how you can multiply two identical numbers together and get a negative result!.