Question

Time taken by a 836 W heater to heat one litre of water from 10 ${}^{\circ }$C to 40 ${}^{\circ }$C is:

• A. 50 s
• B. 100 s
• C. 150 s
• D. 200 s

Answer 1

The correct option is C 150 s

$Q=Pt=ms\Delta \theta$

Given, $P=836W$
$\Rightarrow P\times t=ms\Delta \theta$
$\Rightarrow 836\times t=1\times 4200\times 30$
$\Rightarrow t=\frac{126000}{836}\approx 150s$