Timeline for The relationship between impedance, resistance and resistivity and which are purely material properties
Current License: CC BY-SA 4.0
8 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Oct 28, 2021 at 15:29 | comment | added | The Photon | Resistance of a wire becomes frequency dependent when capacitive and inductive effects change the current density distribution in the wire (cf. skin effect) | |
| Oct 28, 2021 at 9:12 | comment | added | John Rennie | @Chris a component has an inductance when it has an associated magnetic field due to the current passing through it. The inductance is due to energy transfer to and from that magnetic field. Even a straight wire has a magnetic field when current passes through it, but the field is normally too weak to make much difference. Wind the wire into a coli and now you have an electromagnet with a strong field, so it has a much higher inductance. So the sheet in the example you link will have an inductance albeit a small one. | |
| Oct 28, 2021 at 9:06 | comment | added | John Rennie | @Chris That's because a sheet has an inductance as well as a resistance. It is the inductive part of the sheet impedance that is frequency dependent. Under normal conditions the inductance of a sheet is too low to make much difference, but the inductive impedance is proportional to ω and microwaves are very high frequency. That's why in the article you link (about microwaves) the inductance matters, | |
| Oct 28, 2021 at 9:01 | comment | added | Chris | The source microwaves101.com/encyclopedias/rf-sheet-resistance suggests that 'sheet resistance' is a function of frequency. However, it is only the size of the sheet that relates the sheet resistance to the resistance, so this feels like a contradiction. | |
| Oct 28, 2021 at 8:52 | vote | accept | Chris | ||
| Oct 28, 2021 at 8:30 | comment | added | John Rennie | @Chris Yes. The resistance is independent of frequency. | |
| Oct 28, 2021 at 8:25 | comment | added | Chris | So are you saying that resistance is independent of frequency, and it is this that enables one to define a geometry independent resistivity? | |
| Oct 28, 2021 at 8:14 | history | answered | John Rennie | CC BY-SA 4.0 |