P27_018.PDF

(54 KB) Pobierz

Chapter 27 - 27.18

18. In Eq. 27-17, we let ρ =2 ρ 0 where ρ 0 is the resistivity at T 0 =20 ◦ C:

−

ρ 0 =2 ρ 0 −

ρ 0 = ρ 0 α ( T

−

T 0 ) ,

and solve for the temperature T :

T = T 0 + 1

α =20 ◦ C+

10 − 3 / K ≈

250 ◦ C .

4 . 3

Since a change in Celsius is equivalent to a change on the Kelvin temperature scale, the value of α used

in this calculation is not inconsistent with the other units involved. It is worth nothing that this agrees

well with Fig. 27-10.