Transcription of Temperature coefficient of resistivity
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Temperature coefficient of resistivity
Temperature coefficient of resistivity )]TT(1[oo + = )]TT(1[RRoo += T0 = reference Temperature = Temperature coefficient of resistivity , units of( C)-1 For Ag, Cu, Au, Al, W, Fe, Pt, Pb: values of are ~3-5 10-3 ( C)-1 Tslope = )]TT(1[RRoo +=Example: A platinum resistance thermometer uses thechange in R to measure Temperature . Suppose R0 = 50 at T0=20 C. for Pt is 10-3 ( C)-1 in this Temperature is R when T = C?R = 50 [1 + 10-3 ( C)-1 ( C)] = Temperature coefficient of resistivityExample: A platinum resistance thermometer has aresistance R0 = at T0=20 C. for Pt is 10-3( C)-1. The thermometer is immersed in a vesselcontaining melting tin, at which point R increases . What is the melting point of tin?)]TT(1[RRoo += = 50 [1 + 10-3 ( C)-1 (T 20 C)] = [1 + 10-3 ( C)-1 (T 20 C)] = 10-3 ( C)-1 (T 20 C)212 C = T 20 CT = 232 CLight bulbsInert gas (typically Ar) is used to make sure that filamentis housed in an O-free environment to preventcombustion reaction between W and Sir Joseph Swan (1878) &American Thomas Edison (1879).
R=R o [1+α(T−T o)] Example: A platinum resistance thermometer uses the change in R to measure temperature. Suppose R 0 = 50 Ω at T 0=20 ºC. α -3for Pt is -1 3.92×10 (ºC)in this temperature range.
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