enter image description hereI 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.

  • \$\begingroup\$ Sorry, I am unable to enlarge the picture... But it is more visible if you click on it... \$\endgroup\$
    – Michel
    Commented Jun 23, 2018 at 4:26
  • \$\begingroup\$ 1/0 + R is not equal to R. \$\endgroup\$
    – The Photon
    Commented Jun 23, 2018 at 4:45
  • \$\begingroup\$ \$Z = \sqrt{(\frac{1}{0\cdot C})^2 + R^2} = \infty\$ Also, how can you have a negative capacitance? \$\endgroup\$
    – G36
    Commented Jun 23, 2018 at 6:14

1 Answer 1


If w is 0, then jwC will be 0. The reciprocal of 0 is ±inf.

  • \$\begingroup\$ In the context of complex numbers, \$\pm \infty\$ is not all the possible infinities. \$\endgroup\$
    – The Photon
    Commented Jun 23, 2018 at 4:54

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