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I am using an impedance meter to measure impedance in complex form (R-jX) and an RLC meter to measure R & C values in an RC circuit. The value of DC resistance is equal to the R value in impedance equation. My question is whether the R in impedance an ac or dc resistance?

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It's the real part of the impedance at whatever frequency you're calculating the impedance for.

Very often, the \$X\$ component will be proportional to frequency so that in the limit as \$\omega\to 0\$, the impedance is \$R\$ making \$R\$ the DC resistance.

In other cases, \$R\$ also has some frequency dependence. Then the DC resistance is whatever value \$R\$ has when the frequency is 0.

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  • \$\begingroup\$ According to my knowledge, ac resistance is bigger than dc resistance due to skin effect. Also, ac signal is applied when impedance is measured by any instrument. Can we say R in the impedance value is ac resistance? But then again, I am getting the same value when I measure the dc resistance. Note: I am measuring impedance of RC circuit at 1kHz. \$\endgroup\$ – NHB Nov 27 '18 at 17:14
  • \$\begingroup\$ If you're calculating the impedance at 1 kHz, you need to use the resistance and reactance at 1 kHz. If you're calculating the resistance at DC you need to use the resistance at DC. \$\endgroup\$ – The Photon Nov 27 '18 at 17:15
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    \$\begingroup\$ Also, skin effect mainly affects wires, but wires are not the only kind of component that can be characterised by an impedance. If you want to ask specifically about wires, you should edit your question to clarify. \$\endgroup\$ – The Photon Nov 27 '18 at 17:16

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