# rectangular and polar forms

• Jun 12th 2012, 11:44 AM
tomjay
rectangular and polar forms
z1 = 2 + j2

z2 = 1 + j5

z3 = j6

what is Y when :

Y = (1/z1) + (1/z2) + (1/z3)

1/z3 how is that done??????
• Jun 12th 2012, 02:12 PM
BobP
Re: rectangular and polar forms
Multiply top and bottom by $j.$

$\frac{1}{Z_{3}}=\frac{1}{j6}=\frac{j}{j}.\frac{1}{ j6}=\frac{j}{-6}=-\frac{1}{6}j$
• Jun 12th 2012, 11:43 PM
tomjay
Re: rectangular and polar forms
thanks bobp

is this right what ive done so far
1/z1 = 1/ (2+j2) = 0.25 - j0.25

1/z2 = 1/ (1+j5) = 0.0385 - j0.1923

1/z3 = j6 = j-1/6

add them all together
= 0.2885 - j-0.609
• Jun 13th 2012, 12:44 AM
BobP
Re: rectangular and polar forms
Not totally correct, though the decimal values are correct.
The end of that last line $-j-0.609$ would be interpreted as minus $j$ minus $0.609,$ that is, two separate terms. And you have two negative signs when there should just be one.
The correct form should be $-j0.609$ or $-0.609j.$ I prefer the second one though I know the purists will say that the first is correct.
You make more or less the same mistake in the $1/Z_{3}$ line immediately above. Write it as $1/Z_{3}=j(-1/6),$ it's a multiplication not a subtraction.