Thermal Properties of Matter - Result Question 9
9. A centigrade and a Fahrenheit thermometer are dipped in boiling water. The water temperature is lowered until the Fahrenheit thermometer registers $140^{\circ}$. What is the fall in temperature as registered by the Centigrade thermometer?
(a) $80^{\circ}$
(b) $60^{\circ}$
(c) $40^{\circ}$
(d) $30^{\circ}$
[1990]
Topic 2: Calorimetry & Heat Transfer
Show Answer
Answer:
Correct Answer: 9. (c)
Solution:
- (c) Using $\frac{F-32}{180}=\frac{C}{100}$
$\Rightarrow \frac{140-32}{180}=\frac{C}{100}$
$\Rightarrow C=60$
Temperature of boiling water $=100^{\circ} C$
We get, fall in temperature $=100-60=40^{\circ} C$
Centigrade (c) Fahrenheit (F) and Kelvin (K) scales of temperature are related as
$ \begin{aligned} & \frac{C-0}{100}=\frac{F-32}{212-32} \\ & =\frac{K-273.15}{373.15-273.15} \end{aligned} $
