Question

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 $

Answer 1

Answer: (B)

For resistance thermometers
$t=\frac{R_{t}-R_{0}}{R_{100}-R_{0}}\times100^{\circ}C$
Here $R_{t}=5.5 \Omega, R_{0}=5 \Omega, R_{100}=5.25 \Omega$
$\therefore t=\frac{5.5-5}{5.25-5}\times100$
$=\frac{0.5}{0.25}\times100$
$=200^{\circ}\,C$