Transmission Of Heat Question 101
Question: A room is maintained at $ 20^{o}C $ by a heater of resistance 20 ohm connected to 200 volt mains. The temperature is uniform throughout the room and heat is transmitted through a glass window of area $ 1m^{2} $ and thickness 0.2 cm. What will be the temperature outside? Given that thermal conductivity K for glass is $ 320\ kcal/m^{2}\ min $ and J = 4.2 J/cal
[IIT 1978]
Options:
A) $ {{15.24}^{o}}C $
B) 15.00°C
C) $ {{24.15}^{o}}C $
D) None of the above
Show Answer
Answer:
Correct Answer: A
Solution:
Heat developed by the heater $ H=\frac{V^{2}}{R}.\frac{t}{J}=\frac{{{(200)}^{2}}\times t}{20\times 4.2} $ Heat conducted by the glass $ H=\frac{0.2\times 1\times (20-\theta )t}{0.002} $ Hence$ \frac{{{(200)}^{2}}\times t}{20\times 4.2}=\frac{0.2\times (20-\theta )t}{0.002} $
$ \Rightarrow \theta ={{15.24}^{o}}C $
BETA
