# Impedances of a RC circuit

I am working on the question in the image attached. As shown, I have gotten the first question right, although with a bit of trial and error. I was able to solve circuit one on my own, but from there on.

For example:

In circuit two, I found that the impedance is: 1/jwC +R. For w=0, the size of the impedance I think is R, = 10000 ohms, (substituting w=0 into the overall impedance equation I just wrote.) However, the answer is actually infinity, and I do not understand why this is.

I appreciate any help. Thank you for your time.

• Sorry, I am unable to enlarge the picture... But it is more visible if you click on it... – Michel Jun 23 '18 at 4:26
• 1/0 + R is not equal to R. – The Photon Jun 23 '18 at 4:45
• $Z = \sqrt{(\frac{1}{0\cdot C})^2 + R^2} = \infty$ Also, how can you have a negative capacitance? – G36 Jun 23 '18 at 6:14

• In the context of complex numbers, $\pm \infty$ is not all the possible infinities. – The Photon Jun 23 '18 at 4:54