JEE Main 2026 — Jan 21, Shift 1 — Physics solution

JEE Main2026Jan 21, Shift 1Physics

A gas based geyser heats water flowing at the rate of 5.0 litres per minute from 27°C to 87°C.

The rate of consumption of the gas is ____ g/s.

(Take heat of combustion of gas = $5.0 \times 1 0^{4}$ J/g) specific heat capacity of water = 4200 J/kg. °C

Solution

Mass flow rate of water: $\overset{m}{˙} = 5$ L/min $= \frac{5}{60}$ kg/s $= \frac{1}{12}$ kg/s.

Power required: $P = \overset{m}{˙} c Δ T = \frac{1}{12} \times 4200 \times 60 = 21, 000$ W.

Gas releases $5 \times 1 0^{4}$ J/g, so consumption rate $= P / (5 \times 1 0^{4}) = 21000/50000 = 0.42$ g/s.

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