Verified Solution • 2025–26 Session moderate

Q11.1: NCERT Physics - Part 2 THERMODYNAMICS 11.1 Solution: A geyser heats water flowing at the rate of 3.0 litres per…

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often plug $c = 4.2$ kJ·kg⁻¹·°C⁻¹ directly with the water mass in grams, which yields a result 1000 times too small; always match units – use $c = 4.2$ J·g⁻¹·°C⁻¹ when the mass is in grams (or convert mass to kilograms if using kJ·kg⁻¹·°C⁻¹).

A geyser heats water flowing at the rate of 3.0 litres per minute from 27 �C to 77 �C. If the geyser operates on a gas burner, what is the rate of consumption of the fuel if its heat of combustion is 4.0×1044.0 \times 10^4 J/g?

Step-by-Step Verified Solution

**Answer:** Rate of fuel consumption = 15.75 g/min **Step-by-Step Explanation:** Mass of water flowing per minute = 3.0 litres = 3000 g. Heat required to raise temperature:
Q=mcΔT=3000×4.18×(77−27)=3000×4.18×50=6.27×105 J/minQ = mc\Delta T = 3000 \times 4.18 \times (77 - 27) = 3000 \times 4.18 \times 50 = 6.27 \times 10^5 \text{ J/min}
Heat of combustion of fuel = 4.0×1044.0 \times 10^4 J/g. Rate of fuel consumption:
dmdt=6.27×1054.0×104=15.675 g/min≈15.75 g/min\frac{dm}{dt} = \frac{6.27 \times 10^5}{4.0 \times 10^4} = 15.675 \text{ g/min} \approx 15.75 \text{ g/min}
Standard answer using c=4.2c = 4.2 J/g�C: 15.75 g/min .

All Questions in this Chapter

Q11.1 Q11.2 Q11.3 Q11.4 Q11.5 Q11.6 Q11.7 Q11.8

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