Q. An electric kettle takes $4\ A$ current at $220\ V.$ How much time will it take to boil $1\ kg$ of water from room temperature $20℃?$ The temperature of boiling water is $100℃$
A) $0.63\ minutes$
B) $6.3\ minutes$
C) $12.6\ minutes$
D) $12.8\ minutes$
Explanation
(b) Electric power consumed by kettle $P = 220 \times 4W$
Heat required
$H = 1000 \times 1(100 - 20) = 1000 \times 80\ cal = 4200 \times 80\ J$
$P = \frac{H}{t} \Rightarrow H = P \times t$
$\therefore 220 \times 4 \times t = 4200 \times 80 \Rightarrow t = 6.3\ minutes$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.