# AC and DC Resistance [closed]

I have a few questions regarding my task of calculating AC and DC resistances:

1. If a cylindrical conductor is made of two different materials, would the conductor's effective resistance be the parallel combination of two resistors? Or do I just add up both resistances that each material provides?

2. For finding the Impedance $Z = R + jX$ (with $j = \sqrt{-1}$) do I use $R_{dc}$ or $R_{ac}$ for $R$ in this equation?

3. I see in some previous questions on the internet that people are saying that AC resistance is always greater than DC resistance due to the Skin Effect. What happens when we factor in the Proximity Effect too? Does this inequality still hold?

I would greatly appreciate any input for these questions. I seem to be confused with the differences between AC Resistance and Impedance. Thank you in advance!

• Think about it. How can we possibly answer this without knowing how the materials are arranged in the cylinder and between what two points you are measuring resistance. This is not a real question. Nov 16 '12 at 20:43
• Yes the first part of the question required more information, but I don't think this question should be down voted because of it, just request more information. Nov 16 '12 at 22:48
• @OlinLathrop It seems someone is completely lost and trying to figuring it out. Nov 16 '12 at 22:54