A platinum resistance thermometer has a resistance of 2 ohm at 0 C and 3 ohm at 100 C. What will be the temperature when resistance indicates 5 ohm?
Answer (1)
30th Sep, 2020
Hello,
Solution :
The resistance and temperature relation is given by ,
Rt = R0 ( 1+ αt )
By electric resistance thermometer.
R0 - resistance at 0° C
R0= 2 ohm
R100 = 3 ohm
So,
2 =R0(1+α*0)
3 = R0 (1+ α*100)
By Cross multiplication,
2+ 200α= 3
200α = 3-2
200α = 1
So, α = 1/200 = 0.005
Now,
R = 5 ohm
5 = 2 ( 1+ 0.005t)
5 = 2 + 0.01t
5-2 = 0.01t
3 = 0.01t
3 = 1/100 t
t = 3*100
t = 300° C
So,
when resistance indicates 5 ohm the temperature will be 300° C
Hope it helps
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