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??????

Printable View

- Jun 12th 2012, 11:44 AMtomjayrectangular 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 PMBobPRe: rectangular and polar forms
Multiply top and bottom by $\displaystyle j.$

$\displaystyle \frac{1}{Z_{3}}=\frac{1}{j6}=\frac{j}{j}.\frac{1}{ j6}=\frac{j}{-6}=-\frac{1}{6}j$ - Jun 12th 2012, 11:43 PMtomjayRe: 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 AMBobPRe: rectangular and polar forms
Not totally correct, though the decimal values are correct.

The end of that last line $\displaystyle -j-0.609$ would be interpreted as minus $\displaystyle j$ minus $\displaystyle 0.609,$ that is, two separate terms. And you have two negative signs when there should just be one.

The correct form should be $\displaystyle -j0.609$ or $\displaystyle -0.609j.$ 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 $\displaystyle 1/Z_{3}$ line immediately above. Write it as $\displaystyle 1/Z_{3}=j(-1/6),$ it's a multiplication not a subtraction.