Numerical on resistance thermometer.

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?

a. 300° C
b. 200° C
c. 350° C
d. 400° C

Correct Answer : a. 300° C

Explanation :

The resistance and temperature relation is given by R = R₀ (1 + αt) by electric resistance thermometer.
where R₀ is the resistance at 0° C
R₀ = 2 ohm
R₁₀₀ =3 ohm
= (1 + α 100)
Therefore α = 0.005
Now,
R= 5 ohm
5 = 2 (1 + 0.005t)
t = 300° C