JEE Main · 2022 · 26 Jun 2022 · Shift 2 · Heat & Thermodynamics

A geyser heats water flowing at a rate of 2.0 kg per minute from

3 0^{\circ} C

7 0^{\circ} C

. If geyser operates on a gas burner, the rate of combustion of fuel will be _____

g min^{- 1}

[Heat of combustion

= 8 \times 1 0^{3} Jg^{- 1}

Specific heat of water

= 4.2 Jg^{- 1}^{\circ} C^{- 1}

]

Answer: 42

Solution

Heat required per minute to heat the water:

Q = m s Δ T = 2000 \times 4.2 \times 40 = 336000

J/min. If the fuel's heat of combustion is

L = 8 \times 1 0^{3}

J/g, then the rate of fuel consumption is

\frac{Q}{L} = \frac{336000}{8000} = 42

g/min.

JEE Main · 2022 · 26 Jun 2022 · Shift 2 · Integer answer

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