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VK3ABK > TECH 25.05.06 11:37l 52 Lines 1749 Bytes #999 (0) @ WW
BID : 30612_VK3HEG
Read: DL1LCA GUEST OE7FMI
Subj: Resistivity again. (VK3ZRG)
Path: DB0FHN<DB0THA<DB0HDF<DB0ERF<DB0MRW<OK0PPL<DB0RES<DK0WUE<GB7FCR<VK7AX<
VK3HEG
Sent: 060524/0724Z @:VK3HEG.#WEV.VIC.AUS.OC #:30612 [Ballarat] $:30612_VK3HEG
From: VK3ABK@VK3HEG.#WEV.VIC.AUS.OC
To : TECH@WW
Hello Ralph and other Resistors.
My reference for the metal resistivities was 'Reference Data For Radio
Engineers'(ITT) Sixth Edition, Fourth Printing, 1981. These figures were
for metals at 0C, but as Chromium has a low temperature coefficient,
figures for 18-20C should be nearly the same.
I just looked in several other books, and found similar data. Some were
given in SI units as Paul, M0CNL, has written in his bulletin.
From 'University Physics'....
Silver...........1.47 x 10^-8 Ohm-m Only a few and no Chromium but
Copper...........1.72 x 10^-8 Ohm-m close to Paul's figures, and
Aluminium........2.63 x 10^-8 Ohm-m confirming his 0.0000059 T coeff.
From 'Solid State For Engineers' (1958) I found....
Ohm cm x 10^-6
Silver..........1.58 All at 18C except Chromium! Why?
Copper..........1.68 But note the low T coeff.
Gold............2.21
Chromium........2.6 (at 0C) And the same figure for my earlier one
Aluminium.......2.72 from the ITT Handbook.
Nickel..........7.35
Another reference in SI units from 'Physics' by Resnick and Halliday....
Silver..........1.6 x 10^-8 All at 20C and in Ohm-m
Copper..........1.7 x 10^-8
Aluminium.......2.8 x 10^-8 These figures are close to the above but
Nickel..........7.8 x 10^-8 T coeff may be significant for some.
For stainless steel, the ITT HB gives 90 Ohm-cm (0.1 C, 18Cr, 8 Ni, and the
balance Fe).
So, it seems, Ralph, that you will have to accept the ARRL figure as being
the most likely nearest! Why the differences in various references? Surely
experimental error or failure to check calibration, can be ruled out!
73. Dick. VK3ABK.
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