Q. The resistance of the wire in the platinum resistance thermometer at ice point is 5$\Omega$ and at steam point is 5.25$\Omega$.When the thermometer is inserted in an unknown hot bath its resistance is found to be 5.5$\Omega$.The temperature of the hot bath is
A) 100${^\circ}$C
B) 200${^\circ}$C
C) 300${^\circ}$C
D) 350${^\circ}$C
Explanation
(b) For resistance thermometers
$t = \frac{R_{t} - R_{0}}{R_{100} - R_{0}}$ $\times$ $100℃$
Here $R_{t}$=5.5$\Omega$, $R_{o}$=5$\Omega$, $R_{100} = 5.25\Omega$
$\therefore\ \ \ \ \ \ \ t = \frac{5.5 - 5}{5.25 - 5} \times$ 100
$\ \ \ \ \ \ \ \ \ \ \ \ \ = \frac{0.5}{0.25} \times$ $100 = 200℃$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.