Thermal Properties Of Matter Ques 21
21. An electric kettle takes $4 $ $A$ current at $220$ $ V$. How much time will it take to boil $1 $ $kg$ of water from temperature $20^{\circ} C$ ? The temperature of boiling water is $100^{\circ} C$.
[2008]
(a) $6.3 $ $min$
(b) $8.4 $ $min$
(c) $12.6 $ $min$
(d) $4.2 $ $min$
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Answer:
Correct Answer: 21.(a)
Solution:
- (a) Heat required to raise the temperature of $1$ $ kg$ water from $20^{\circ} C$ to $100^{\circ} C$ is given by $Q=ms \Delta \theta=(1 \times 4200 \times 80) J$
Power of kettle $(P)=VI=(220 \times 4) W$
$\therefore$ Time taken $=\frac{Q}{P}=\frac{1 \times 4200 \times 80}{220 \times 4}$
$ =381.81 $ $sec=6.36$ $ min $
BETA
