Question

11.3. The electrical resistance in ohms of a certain thermo-
meter varies with temperature according to the approximate
law :
R = R, [1 + 5 x 10 raise -3 (T-To)]
The resistance is 101.6 ohm at the triple point of water, and
165.5 ohm at the normal melting point of lead (600.5 K). What is
the temperature when the resistance is 123.4 12 ohm? ​

Answer 1

At triple point temperature =273.16 K and resistance =101.6Ω and normal temperature T 0= 600.5 K and resistance =165.5Ω

As per approximate law R=R 0

[1+α(T−T 0 )

Now when resistance is 101.6Ω temperature T=273.16 K

101.6=165.51+α(273.16−600.5)

α = 327.34×165.5

63.9=1.17×10 −3

Now when resistance is 123.4Ω then temperature T is: 123.4=165.5[1+1.17×10 −3

(T−600.5)]

T= 165.69

123.4 +600.5

T=601.24K