I have an exemption test for Circuits in 2 days and I've been doing practice problems.

I came across this and am very confused how the reactance switches signs in the simplify step.

Can someone explain this to me or is it a typo on that site (Like I hope it is.)?

Thanks.

 

Did you mean the impedance?

2k - 250 = +1750

 

No, I mean just the reactance part of the impedance in the step that converts to milli instead of kilo. It becomes 1/3m + 1m - j0.57m

The signs on the DC resistance stayed positive and the reactance due to the inductor/cap flipped (It does come out as the right magnitude).

EDIT: Oh Snap! I got it...I think. It is (1 < 0)/(1750 < 90) which makes it become -90.

 

I'm guessing your question is how does one get .....

\(\frac{1}{j1750}=-j0.571m\)

Are we agreed that 'm' just stands for \(10^{-3}\)

So

\(\frac{1}{1750}=0.571 X 10^{-3}=0.571m\)

Also remember that for the complex operator 'j'

\(\frac{1}{j}=-j\)

combining these two concepts

\(\frac{1}{j1750}=-j0.571m\)

Or you do it like you did in your EDIT .....