Question

A geyser heats water flowing at the rate of 4 litre per minute from 30°C to 80°C. If the geyser operates on a gas burner then the amount of heat used per minute is

• A. 9.24 × 105 J
• B. 6.24 × 107 J
• C. 9.24 × 107 J
• D. 6.24 × 105 J

Answer 1

Answer: (A)

9.24 × 105 J

Answer 2

: here, volume of water heated = 4 litre $\min ^ { - 1 }$

1 litre = 1000 g

Then mass of water

$= 4 \times 1000 \mathrm {~g} \mathrm {~min} ^ { - 1 }$ $= 4000 \mathrm {~g} \mathrm {~min} ^ { - 1 }$

Rise in temperature $\Delta T = T _ { 2 } - T _ { 1 }$

$= ( 85 - 30 ) ^ { \circ } \mathrm { C } = 55 ^ { \circ } \mathrm { C }$

Specific heat of water

$s = 4.2 \mathrm { Jg } ^ { - 10 } \mathrm { C } ^ { - 1 }$

The amount of heat used

$\Delta Q = m s \Delta T$