Question

A $2100\text{W}$ continuous flow geyser (instant geyser) has water inlet temperature $={10}^{\circ }C$ while the water flows out at the rate of $20\text{g/sec}$. The outlet temperature of water must be about
(Assume that time lag between inlet and outlet flow is $1\text{s}$)

• A. ${20}^{\circ }C$
• B. ${30}^{\circ }C$
• C. ${35}^{\circ }C$
• D. ${40}^{\circ }C$

Answer 1

The correct option is C ${35}^{\circ }C$

Water flow rate $=20\text{gm/sec}$
For $1\sec$, energy supplied by the geyser is $P\times t=2100\times 1=2100\text{J}$
Let $T$ be final temperature of water
$2100=20\times 4.2(T–10)$
$T={35}^{\circ }C$