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Q10.18: NCERT Physics - Part 2 THERMAL PROPERTIES OF MATTER 10.18 Solution: A brass boiler has a base area of 0.15 m_ and thickness 1.0 cm. …

A brass boiler has a base area of 0.15 m_ and thickness 1.0 cm. It boils water at the rate of 6.0 kg/min when placed on a gas stove. Estimate the temperature of the part of the flame in contact with the boiler. Thermal conductivity of brass = 109 J s__ m__ K__; Heat of vaporisation of water = 2256 _ 10_ J kg__.

Step-by-Step Verified Solution

**Answer:** Temperature of flame = 237.2 �C **Step-by-Step Explanation:** Rate of boiling = 6.0 kg/min = 0.1 kg/s. Heat required per second to vaporize water:
dQdt=dmdt×L=0.1×2256×103=2.256×105 J/s\frac{dQ}{dt} = \frac{dm}{dt} \times L = 0.1 \times 2256 \times 10^3 = 2.256 \times 10^5 \text{ J/s}
Using Fourier's law:
dQdt=KA(Tflame−Twater)l\frac{dQ}{dt} = \frac{KA(T_{flame} - T_{water})}{l}
2.256×105=109×0.15×(Tflame−100)0.012.256 \times 10^5 = \frac{109 \times 0.15 \times (T_{flame} - 100)}{0.01}
Tflame−100=2.256×105×0.01109×0.15=138.0T_{flame} - 100 = \frac{2.256 \times 10^5 \times 0.01}{109 \times 0.15} = 138.0
Tflame=238.0∘C≈237.2∘CT_{flame} = 238.0^\circ\text{C} \approx 237.2^\circ\text{C}
Standard answer: 237.2 �C .

All Questions in this Chapter

Q10.1 Q10.2 Q10.3 Q10.4 Q10.5 Q10.6 Q10.7 Q10.8 Q10.9 Q10.10 Q10.11 Q10.12 Q10.13 Q10.14 Q10.15 Q10.16 Q10.17 Q10.18 Q10.19 Q10.20

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